Here's a pretty crappy Paint rendition of the guts of the planned Mach Goon. The blue is the nose cone, which has a nose weight, eye hook, streamer, shock cord (kevlar), and kevlar heat shield inside it. The red with grey closures is the Aerotech 38/240 reload case. (The Cesaroni Pro38-2G casing is 1.17" longer and thus would not fit).
I don't have any 38/240 motors in TIRASP (to be corrected tomorrow), but on 29/240 motors, it simulated to Mach 1.3 and around 5000 to 8000 feet. Awesome performance for a Goony, and yet still plausible to recover if I put enough tracking powder in.
Since the recovery system is stored inside the hollow nose cone, almost the entire 7.5" long body tube can be used to hold the motor, which is 5.7" long not including the closures. Retention would simply be a few wraps of making tape. The ejection charge would be perhaps 1/10 of the supplied charge to simplify retention and recovery system needs; the remainder of the charge holder space would hold extra tracking powder.
I'm planning to buy 3 Baby Berthas soon with a motor order. One will be the Nike Goon, a second the Mach Goon, and the third yet unknown. It'll fly within a few months on a measly B6-4 for a test flight, and then on an H242T reload at NERRF.