They all should have their own bucket. You'll need the lateral room for growth and some of those will be very nute and water hungry so multiples can cause issues. Not to mention the room that can be needed just for the root mass. Below is a green chile pepper I grew a little while back. There wouldn't be enough room for more than one plant.

Wow! That's nuts!

So I assume if I want to start seedlings and then transplant them to soil outdoors, I can do 4 per bucket?

I wouldn't. They will grow into each others roots and detangling them is worse than detangling 9 year old girls' hair - everyone gets hurt. If you keep them seedlings and don't le them grow more than that (very simple root system), I would use a nursery to grow a boatload of them at once. But you wouldn't need hydro to do that.

Got it!

You would be supprised what a very sharp knife and roots can endure. the growth is worth going hydro and if you are transplanting into soil go for it. Whether 8 in a bucket or not they can be cut, split, and transplanted in 8-12 weeks no problem at all. Having 2ft plants in 8 weeks is worth it to me at least.

http://www.tractorsupply.com/tsc/product/koch-industries-sisal-twine-1-ply-x-2250-ft-tube?cm_vc=-10005

Couldn't find specific roll i bought but one purchase would last near a lifetime even if using for staking, lighting, netting.

Here it is...just finished transplanting.

Beautiful. Keep us posted :-)

I'm stoked. The cukes and bean already had roots that were about 2" out of the rockwool. Two days after sprouting. Crazy.

Nutes are still my biggest mystery. I want to understand that aspect.