Here's my L3 cert flight at AIRFest, the airframe is a pretty standard 4" all fiberglass scratch build. I had a Featherweight GPS, Raven4, and Stratologger CF on board. This airframe is really the booster section of a 4-to-3" min diameter two stage design and launched on an M650 which is actually what the sustainer will use. The motor attaches to an Aeropack min diameter retainer and i use an adapter ring set for centering and thrust. Now that I'm certified, I plan to launch the full stack (N to M) at BALLS next year (hopefully).