I personally think that is a little too small. They need more ground room than vertical room, but it may work.

As for not using an UTH, what you can do is to prop your tanks up on some 2x4's. Cut down a 2x4 so that it is the width of your tank, then set your tank on those. Cheap and easy solution. I would advise against a lamp if possible. I think that belly heat works best for corns.