On your videos, you usually make great motor choices, maximizing use of your field, but most of them seem to stay out of the canal. Rocketry if one sport where you do NOT want to “knock it out of the park!”
For multistagers, I hesitate to “go small” on the booster (although I wish I had on my CiCi2, it staged at about 200 or 200 feet, going horizontal, and the sustainer glider was never seen by my eyes again!). But I always go small on the sustainer for first flights, in fact sometimes I will adapt down a motor size.
This reduces the weight of the stack (so you get more end rod/rail velocity for same booster motor), and since the sustainer is already at a stable speed at separation (it better be, if not the black powder sustainer motor is not gonna kick in fast enough to help), so especially for first flights you don’t really need much thrust on the sustainer, assuming a short delay motor if you go really low (like replacing an 18 mm motor with an A10-3T.)