Thank you again for everyone's replies! I'm so glad I asked.

I had not given thought to room temp. I keep the snakes in my room because it's the quietest and the girls friends are not allowed in there. Upstairs tends to run warmer in the summer and cooler in the winter. Right now it works out fine but now I'm wondering about winter temps. I had no idea that you could do belly heat and back heat and I actually may need that if upstairs is too cool.

I am no longer considering building one. I want to make sure the heat tape is done properly especially if we need two kinds of heat. Also rethinking size. I know 41quart for adults but I have a female that is not quite 500 grams and a new baby bee that is 70 grams. I'm guessing I won't need adult tubs for awhile and I want them to feel secure. We have had Kasi the female for almost two months so I am ways away from even giving a thought into someday breeding.

Tank vs Tub. I loved seeing this dicussed! . I'll admit having them in a rack with the sides covered did give me pause but I did not think about them living in a burrow and honestly they are in hides most of the time anyway or I could not have sides on the rack.
I think what is suitable for some snakes would not be good for others. I know Kasi would not be happy in a tank.

Talked to my husband a little this evening. Can anyone chime in about using a heat cable? Does the flexiwatt get damaged over time with it being on the bottom of tub and getting rubbed by sliding the tub? Where do you have your tape for belly heat and if you also use back heat for your tubs?