I'm not sure I understand how you are going to tie the skippy into the waterfall. Your pump takes the water to the highest level then it's all down hill from there. So if you want the water to flow from the skippy to the waterfall, the water has to come out of the skippy above the waterfall level. My big filters are both sunk partially into the ground. I have one smaller filter made out of a garbage can that does an amazing job so a smaller skippy can work. It's the first filter I get going in the spring.

Sherry, your description is perfect. Perhaps you missed Catherine's concern about spread out flows (including a flattened constriction) that was in another thread. Your description points to why a constriction would be incompatible.
Catherine, I believe most skippys are partially below ground to hide them. I don't think it matters unless perhaps the ground insulation moderates temperature. The stress or flow rate of the pump is a function of total height first and length of tubing second. I doubt that the 'down then up' flow of a skippy is relevant except for the added length (and likely smaller tubing size in the skippy tubing). If you use a skippy, I suggest you forget the constriction approach and focus on the flatness, sealing sides and bottom to prevent water loss, and level of the spillway to preserve total flow over the rock.

Please forgive my slowness in understanding this. If I have a decent pump, shouldn't it pump water from the skippy UP to the waterfall? I should clarify that all I have for a waterfall is the tubing in-between some rocks.
And as far as the tubing.......if I have 1/2" tubing going into the skippy, don't I have to have a larger tube coming out of the skippy? I really like the type of small waterfall that a 1/2" tubing allows (I've tried 3/4" and it's too forcefull).....but I also don't want water overflowing out of the skippy.
Again, I apologize if I'm slow with this, or not understanding something that you've said.
I appreciate your help!

If I have a decent pump, shouldn't it pump water from the skippy UP to the waterfall?

Yes.

It had not been clear that you did have an adequate pump. The other threads suggested that you had minimal flow that might not even spill evenly over a flat spillway and would require a flattened tube to more widely distribute this miniscule flow.

if I have 1/2" tubing going into the skippy, don't I have to have a larger tube coming out of the skippy?

Yes; except I wouldn't even call it 'tubing' for the Skippy output. The outflow from the Skippy is usually something like a shower drain connector.

If you have too much flow, don't constrict it at the outflow. Divide it before it gets to the Skippy. Put a T tube after the pump with a valve on one or both outflows and let the excess stay in the pond.

Thanks chas.
I do have a small pump in there now.........330gph. It seems to be sufficient for my small pond and waterfall. I tried it with 3/4" tubing, and it was too much flow at the waterfall......so I'm back to the 1/2" tubing. I wonder if I did divert some of the water at the pump, maybe then it wouldn't be enough flow for the skippy/waterfall? I did try a store-bought waterfall spillway, and the 1/2" tubing did fine with it, but I have since decided that I like movement of the water over the rock waterfall better with just positioning a hose between the rocks. I guess I need to study up on my physics. haha So, just to repeat myself.....if I did divert some of the waterflow right after the pump, does that mean I could then use a 1/2" tube for the skippy outflow? I suppose a lot of this is just trial and error. I've seen a couple You Tube skippy videos that show if you make 2 outflows, you can keep the skippy from over-flowing. I suppose I could do that, with 2 runs of 1/2" tubing that I could still position in the rocks. Maybe I just can't have a skippy for my 300 gallon pond, without using at least a 3/4" tube coming out of the skippy.
And since we're talking physics?? ....why does one even need a bigger tube coming out of the skippy? Why isn't what goes into the skippy=what goes out? (or at least the rate of flow).

Is this clear as mud now? ;)
Thanks chas!

Why isn't what goes into the skippy=what goes out?

It is. If everything worked perfectly, there would be no problem. We are just attempting to play it safe. If your outflow gets slightly clogged, you are immediately in trouble and the whole Skippy will overflow outside your pond. If your pump cutoff switch (if you have one) fails, all your water gets pumped out and perhaps your pump burns out from overheating or water lubrication failure, and your fish (if you had them) die.

Would your outflow get clogged? With a half inch pipe (3/4" too); Oh you betcha! Even if you didn't put a (or some some) plants at the top of the Skippy (it looks nice and hides the skippy), other crud is going to fall in there or come up from stuff in the Skippy. BTW, an even better theoretical solution would be to cut a big notch at the top of your garbage can and glue your red scoop (back cut off) into it for a completely open spillway. It would actually probably leak and then completely crack away with disasterous results, so it is not a good practical solution

Cetherine, Chas has explained everything very well. I just have a question about your original post: if you sink your skippy into the ground, is the opening of the outflow going to be above the waterfall or below the waterfall?

1)If the opening is above the waterfall, then sinking the skippy into the ground would not Increase the load of your pump. For this arrangement, if you can reduce the infow to the skippy(like use a diverter) enough, use either 3/4 or 1/2 tubing should give you the same effect. There are diverters that you can adjust how much to divert to where.

2) if the outlet opening is below the waterfall, then you are talking about an enclosed system, you are going to relay on the pressure inside the skippy to pump the the outflow water higher to reach the water fall.

The second arrangement not only makes your pump work harder, it will also put a lot pressure inside the skippy.

Thanks Chas and Sara. I hadn't even thought about the outflow getting clogged. Lots to think about. Thanks again for your input.

Sara, the outflow of a Skippy is always either at or above the waterfall. I don't think anyone has ever designed a sealed Skippy.
And Catherine, we haven't really covered whether a Skippy or other filter is really needed. I'm not sure that a filter will stop any need to clean out your pre-filter at the pump. You still need something to prevent crud getting into the pump, and you would occasionally need to remove that stuff. We also didn't answer your question about the five or 10 gal bucket. Most Skippys are larger. My Skippy is considered small (Skippy calls it a 'mini-me) and it is a 20 gal plastic garbage can. I think a 10 gal container would work ok. You would want to keep the plumbing pipe to 1/2" max because you are attempting to get swirling (via jets of water) at the bottom of the container.