Here's how I added an aluminum ion arm and a clippard valve without drilling cutting or gluing to the pack:
1)Mill out holes in bottom of the aluminum ion arm to fit over the pegs
2)Mill out channel so I can glue in two recessed magnets
3)Cut the hex bolts on the ion arm down so they don't protrude
4)Tape a metal strip to the pack where the ion arm attaches using automotive double-sided tape.
Holds securely and sits flush. Next experiment is to see if I can mill enough out of the back of a clippard valve to fit over the plastic cylinder that most people are cutting off.
You would think that Hasbro would have made it so you could just unscrew the fake valve and install a real one, but they didn't. There are two issues:
1) the screws are smaller than the ones on a real valve
2) there's a 17mm cylinder of plastic sicking up where the valve installs.
Easy thing would be to just cut off the cylinder and drill the holes bigger, BUT I don't want to permanently modify my pack, so here's how to do it the hard way:
1) Dismantle your clippard valve, pull all the guts out, this is done by unscrewing the aluminum cap from the plastic body. Different valves may be slightly different, I'm using a modified 4 way valve that I machined a knob for to look like a R331. In the end you'll need to figure out a way to attach the knob back onto the valve with the guts removed... I just epoxy my knob in place.
2) Using a dremel cut out an approximately 18mm hole in the plastic base so it will fit over the cylinder of plastic on the pack.
3) To allow for the smaller screws, tape off the bottom of the holes and fill them halfway with epoxy. These can then be later drilled out for the smaller screws. You'll also need to slightly enlarge the screw holes at the front of the clippard valve so the hasbro screws can recess into the hole. Just be sure not to enlarge more than the diameter of the clippard screw screw heads, as these will cover the hole in a later step.
4) Reassemble the valve, glue the adjustment knob in place using plumbers epoxy (careful to center it perfectly), attach to the pack using the hasbro screws.
5) Cut down the clippard screws and glue them over the holes containing the recessed hasbro screws (must be done AFTER the valve is installed on pack).
To return to stock, you just need to remove the clippard screwhead caps that were glued on, and then unscrew the valve from the pack.