Thanks everyone for your input and advice! Now I just need to decide about buying one or trying to convince my husband to build one.

I was looking at this one

http://www.reptilebasics.com/iris-cb-70-rack

But after reading Andrew's response and more searching it looks like 41 quart is the way to go. So now I'm looking at Animal Plastics 1860/1960 4 tub rack but I have a almost 500 gram female and 70 gram male. I think Kasi would do well in larger size but what would I do about the male? I'm guessing in his 16 quart tub he would slide right in till he is ready for a larger size and just keep the lid on? What about the heat tape? Can we just put it on the 16 quart and redo the tape when we need to size up? Sorry if it seems like a dumb question but this is new territory for me.

What racks do you have/recommend?