I finally got my body cast. I use Plaster of Paris for all my casting. It's cheap, and easy to use. It does have one downside though, without reinforcement it's not very strong. It tends to chip and crack easily. There is a simple solution to this though: Elmer's Glue. You can buy it by the gallon at stores like Home Depot. I mix it in at about 3% using the TLAR method(the looks about right). It makes the plaster much stronger. It also extends the set-up time which is very important when mixing such a large amount of plaster.
I made a mold stand that is the exact width I want to end up with. I also put shims on the narrow sides, and shims under the bottom of the mold. Without all this, the mold will bow and flex, and you casting will end up all warped and twisted. My body is actually about 3/8" to short too. Using duct tape around the perimeter of the mold allows me to extend it, making the whole thing taller. I used clear packaging tape to cover the rest of the holes in the mold(it leaves a smoother finish than duct tape).
Anyone who tells you that you can't mix 25lbs of plaster in your kitchen is lying
The set time on PoP is around 20 minutes, and I did it in two pours. I just can't mix it fast enough to get it all in one. By the time the second is mixed up, the first is just starting to set. Fortunately, plaster sticks to it's self very well. DON'T pour any down the sink, plaster hardening in your pipes is a very, very bad thing. Just leave any extra in your mixing bucket. Once it's set, the whole block will pop right out. It's also best to mix your plaster when your wife, girlfriend, or mother is not home