It has to be no bigger than 16 inches long at that scale but my math is probably wrong though. I did a 29mm single deploy scratch version a few yrs ago
What method are you using for booster recovery? The reason I ask is that booster by itself will be very stable so there won't be any tumble recovery, it will require a parachute or it becomes a lawn dart. I would convert at least one if not two of the booster motor tubes into parachute bays at the top and use a short delay motor instead of E12-0 in those two tubes.All "E" size engines. First Flight I will try; Booster: (4) E12-0, Sustainer: (1) E16-3. Comments/Suggestions/Recommendations please.
Personally I would use two 18" parachutes ( one in each of the two tubes you chose) in case one doesnt deploy. Stable boosters stage pretty well as the booster continues on a ballistic path as the sustainer accelerates away at least until the chutes deploy.I thought of using metallic streamers in booster tubes 2 and 4.
I have a much smaller SA-3 Goa fantasy/sport scale that uses rear eject and is flown with a cluster of 2x18mm ( typically a c6-5 and a c6-3) and a central 24mm D12-0 in the booster and a single D12-5 in the sustainer. The flight profile is similar to what you are building due to the stability of the booster. The D12s are gap staged similar to what you are doing, only they are both on the centerline. When I get a chance I will link the build thread on it along with the lessons learned.Thank you "rharshberger"! The thought of using (2) E12-0's in booster tubes 1 and 3 for the booster separation and (2) E12-3 +/-'s in booster tubes 2 and 4 for the booster recovery units is very good suggestion indeed.