I might think on a design that will hold both. I think it may be possible the 32s are about 1/2 the size of the 41s. Double check but I think two 32 side by side and about the same width as the 41 sideways. Might work if the sizes jive.
Personally I would look at PVCx I believe proveer is in GTA they are great. They will cut it to size and it is easily screwed. Melamine too it is just really heavy.
Yes to the t-stat but I would look at the herpstat especially as it is a fair bit cheaper than the VEs in Canada and have more safety features. I have bought a number from spyder robotics direct, the shipping is fair and I have only paid tax no duty or handling.
One other point if you are planning on breeding professionally (legally selling) you may want to rethink the flexwatt. It is very very expensive as legally in a commercial venture it needs to be wired by an electrician. You can buy heat cable and it will work just as well it is pre wired and csa or ul approved and legal. It can be plugged into a bar but a custom wired cable with outlets every 6 inches or so might be easier.