OK, here is the run down on the torsol casting... you have to seperate the original torsol apart in order to cast both halves. You are actually making two molds, on for each half of the body. Almost nobody does this because the way that the halves are sealed. They are sonicly welded together, so the only way to seperate them is to cut them apart which in most cases destroys the body. What Glassman6, Bantha5 and my self do is make a two part mold of the body halves together. Now for those who do want to cast two halves, there are at least two safe ways to go about it. One way is to brush in the plastice resin into the mold in stages, causing a shell. The more palstic you put in, the thicker the shell. Once you have the desired thickness, clean the halves, place the limbs and head and glue the halves together. The other method is to pour liquid wax into the mold all the way to the edge. Let it cool and then put the two halves together. If they do not fit, shave off the excess until they fit. Now with a wax pen, start carving out the wax to hollow it out. Using old model kits, find a male and female peg that would make the locking mechanism. Fit the two halves again for one last alignment check and then make a new mold of the wax casting. From here you will make the plastic cast and then reassemble the figure. In either case, you are looking at a very labor intensive project and you probable only want to do a few important customs to venture into such a costly and time consumming project. This is a professional level stage of toy production and is normally way to advance for the casual hobbiest. But, if you have the time and money to invest into this area of toy production, you could turn out professional looking customs.
I hope this will help you and any others out there that maybe thinking about doing this.