At DART for LPR we mount cheap import 1/2" drill chucks to inexpensive photo tripods using a 1/2-13 x 3/4 bolt. Just drill/tap the bolt head head for a standard 1/4-20 photo tripod stud. Takes 5 mins to make, has a fully adjustable launch angle, and lasts for years. Blast deflector is a 22 cent Home Depot 4x4" ceramic tile with a 3/16" or 1/4" hole drilled using a masonry bit. The 1/2" chuck will accept anything up through a 10mm MakerBeam.
If you're doing a rack style launcher you'll want to add some kind of ball-joint angle adjustment. Unfortunately even the wimpiest ball joint costs more than the drill chuck, making independent pads on tripods look much more attractive given the other advantages.
