My initial plan was to handle stage separation and booster deployment from an altimeter in the ISC (this booster is single opening, so if it did DD I'd use a Chute Release for the main), and handle ignition and sustainer DD from the sustainer's avionics bay. I'm waiting to receive my Black Monday order from MW so I haven't seen exactly how big the RRC3+RTx ends up being, but I'm hoping that will fit in the 54mm x 7" bay. As you point out Cris that does bring up the question of how the ignition wire will break during main separation, this is another sustainer topic I'm curious about, I'm hoping there's some reasonable connector that won't come undone during booster acceleration but would ideally disconnect before damaging the attached wires so that it could be reused without having to replace every time.
On a bigger sustainer I'd be all for making a hatch in the motor area and putting a staging altimeter down there (ideally both separation and ignition), leaving the booster and sustainer with typical DD altimeters. But no way there's room for that in a 54mm tube with 38mm MMT.
Cris, you don't happen to have anything that would do a burnout + X sec charge firing (or else launch detect + X sec), followed by apogee, would you? If not, any chance a future Quantum update could do that? Would be nice if I didn't need one of the fancier >2 output altimeters in the booster when it only needs to fire two charges, it's just not the usual apogee+main charges.
FWIW, I did pretty detailed length/weight measurements on every part in my Double Shot kit to make my starting OR model. Attached is what I have that is purely RW/Madcow's kit, no personalization yet. The 4 Cg-customized parts are the ones I figured wouldn't be balanced, like the NC, transition and slotted tubes, all other weights were set by adjusting the material density for each item. 124oz of bits and 100" of length makes it my longest and heaviest rocket so far, also, of course with recovery, electronics and epoxy it will only get heavier. It occurred to me that the third 54mm coupler bulkhead
may have been intended to seal off the NC coupler rather than as use in the ISC, but then it would leave nothing to seal off the 54mm coupler tube in the ISC which seems like a bad idea to me. So I have it placed down in the ISC as per my drawing above.
View attachment Stock Rocketry Warehouse Double Shot.ork
Edit: BTW, OP if you'd rather I make my own thread rather than adding to yours just let me know. No intention to hijack, but I also figured I wouldn't create a 'competing' thread unless you wanted this one to be specific for yours.