Cage Dimensions

I'm seriously considering making a display wall of cages for my BP's. First off, because I know if I don't say it someone will, I realize BP's are not display animals, that i'll never see them, etc. I also realize it may be more difficult to maintain humidity and temps than it is in the rack they are in now. I'm willing to take the extra effort.

What I'm really wondering is size, strictly from a material efficiency standpoint. With the materials I'm using, it would be MUCH more cost effective to do 4 foot long cages divided in half than to do 5 or 6 foot cages divided the same. So my question is this:

Is 20"x24" (floor space) too small for an adult ball python? If you could have any size cage for your BP's, would it be much bigger than 20x24? My other, less cost effective option is 20"x36".

Money really isn't a huge issue, but if the smaller size would be more comfortable anyways, why waste time, money, and materials building it bigger, right? Thanks in advance for your thoughts!

They say you want a tank that the snake can stretch 2/3's of it's body across.
For babies they say a small because it makes them feel safer.

I plan to have the display wall myself. I currently have 2 40gal tanks on a table I built 80"x24" and plan to build up as my collection grows. The 40gal tanks are 36"x18"x16" and I feel they will work for the life of the snake.

Don't buy the pet store zilla tanks. They are poor quality! The screen for the lids come undone and the floor cracks over the UTH's.

My brother has had his for 11 days and this has happen. he doesn't have anything on the screens and a rheostat on the UTH set at 89 degrees. My tanks the screens are coming undone after 21 days and I had to run a bead of silicone around plastic seam of lid. Also the silicone factory seams are tearing off from inside the tank. I don't have any cracking yet under my tanks but have my eyes glued on it.