good luck it sound like it will suit you well.
http://forums.gardenweb.com/forums/load/sqfoot/msg0617592032032.html?16

Here is a link that might be useful: hope this helps

Fill the 12" boxes with Mel's mix, without putting any gravel in the bottom. You'll be glad you did.

EG

Here is a link that might be useful: My garden blog

Woohoo! You'll love SFG.

Fill the boxes with 12 inches of mix. It's pricey, but you'll love the results.

Don't feel pressured to go with a 4x4 setup. If you're running trellises, it's a pain to set up individual trellis systems on each box. You can go longer, but not necessarily much wider since it will be difficult to reach the inside squares. You also don't have to put them in an exact row with spacings between each. Here's my setup beore I filled the boxes:

The fall is a great time to start. It's when I did as well. Build a small box or two to start with this fall, just keep in mind what you'd like your overall plan to be so you don't wind up moving them later.

Ribbit,
I love your set-up. Very artistic.
Keski

Thanks, keski, but it's Granny that set her boxes at an angle and made me realize things didn't have to be in blocked rows. I have such a small space that I had to put as much as I could and minimize wasted pathway space. I had the two small square boxes first and then things grew. There are even two additional boxes in teh second picture than there were in the first.

The problem with my setup is that you need to be REALLY careful about shading. The peppers can't go where they are this year because of that, although the okra didn't seem to mind so much.

Here is a link that might be useful: The Corner Yard

I agree with EG. Fill the entire 12 inches with Mel's Mix. The plants won't complain if they have more root space and nutrients available. :)

Here is a link that might be useful: Kim's Garden

LOVE your setup, ribbit.

To the OP, I would suggest lasagna gardening the bottom six inches and then filling the top with mel's mix in the spring. Now would be the perfect time to start. Check our the FAQs over at Soil, Compost, and Mulch for more info.

My raised beds essentially are lasagna gardens.

If you lived somewhere rainy, after the nearly 7" of rain we had in July, I started to wonder if they hold too much water, but in UT I'd bet you'd be ok.

Here is a link that might be useful: Tales of a Transplanted Gardener

I think that the quality of Mel's Mix depends on the quality of the compost used. If you can find and use very good quality compost, I think Mel's Mix can be great, but if you skimp on the compost that is used it can be much less than ideal and sometimes problematic.

Good gardening, Mary