Remove Shell First
I like to remove the stylus first then remove the shell.
Once the shell is removed and you are ready to pot the body remove the white plastic ring on the rear pin, this allows the body to sit in place correctly and you can re-install it after the epoxy sets.  Click on picture to enlarge, you can see the lead shot sitting in the epoxy in the front of the body that is propped up in the back. This level of epoxy is how much epoxy I use.
Set body on top of lead to give proper angle.
Tape the back closed, prop the back up (a toothpick will work), install lead, drip the epoxy in until the lead is just covered, install cartridge so the front sits on top of lead, let dry. 
Be sure to do any clean up before the epoxy dries completely hard, I use rubbing alcohol and a Q-tip if I need to clean any epoxy. When the epoxy is fully set remove the tape and install the white band back on the pin.
Finished SC35C's with the Paradox Pulse Universal body
There are other cartridges you can pot with the Paradox shells
A few of the finished products. This is a great place to start and then change the stylus. My favorite affordable stylus is the Shure N97XE. I have tried a few of the $20- to $30- styluses from Ebay and they are better than the stocker which is not very high quality but you can scratch with it!
Any type of epoxy will work, I like it runny and slow setting so I have lots of time to work, but I usually do several at a time, so its your choice. Have fun with these projects and get creative!
Mounting area is .398" wide x .725" long x 0.11" deep. You can also attach to the outside dimensions (.725" wide x .8" long x .232" high) but would cover the screw holes making you adjust the screw height so as to not poke through to the cartridge.
Body weight 4.2 grams for body, add lead 4.5 grams, add stainless screws 5.5 grams total added weight less plastic body 0.8 grams, epoxy should be negligible.
Cartridge (SC35C) angle in stock body 13 degree, with lead support in Pulse body 12 degrees.
These cartridges were done by a great customer of mine. He put his own spin on them, notice the other lead he uses, and they are terrific. If you want to try something different go ahead and then send me some pictures, I would love to see your process. Click on pictures to make larger.

I have provided dimensions so you can measure any cartridge you may be thinking of installing into this body.