I say for belly heat, 4" flexwatt will work for all of those tub sizes. My Rack holds adults, hatchlings, and juvies and I use 4" for it all. I am not very good at building anything.. I was very intimidated by the whole flexwatt thing, too. But if you follow the tutorials you will do just fine.
thanks man! thats the main thing I needed to know. Thank you all for helping
1.0 Pastel 09
0.1 Pinstripe 13
1.0 Champagne 13
0.2 Pastel 13
0.1 Normal Het Albino 13
1.0 Albino 13