I've tried several different setups over the years. My first was 24w X 16d X 48t melamine. I had great success with it, but rarely observed adults moving to lower perches. The only time this happened was with gravid females.
My second set was 24w X 24t X 16d melamine. Again, I had great success with these and actually bred more animals in these than with any other cage I've used. I have always heated with lightbulbs and have never had a problem. The animals have direct contact with the lights if they want, but I have never had an injury because I choose my wattage wisely.
My next set were 20" pvc cubes. These are ok, but do not offer substantial insulation in cooler rooms. Again, I kept the largest of the large chondros in these with equal success. They do the job as long as you can tweek the entire room, which can sometimes cause problems during breeding season.
My latest series are 30x20x20 and 40x20x20 melamine. In my opinion, the 30x20x20 is the perfect size for even the largest adults. I built my 40s because my 20 cubes stack perfectly on top, side by side. I honestly think they are overkill and are so far the most difficult to tweek as far as humidity. I would even go as far to say a 24" cube would be the perfect overall size for adult chondros.
I've also used glass aquariums with modified lids for years. To say aquariums will not work is totally false. Two of the most successful breeders in the world use glass aquariums. If you take the time to make them work, you should have no problems.
It's an age old debate and nothing is stone. Do what works for you and more importantly your animals. They are what should be comfortable.