Fly more than once, activating different drag amounts. Build a model. Do it empirically, but not real time. Dig into openrocket add-ins and build one to do a variable drag profile, a bit like the way someone built an add-in to do winds by altitude. And before someone notices and asks, the V discontinuity at ~1sec is a booster seperation event. The sustainer didn't light (open circuit at timer - I need to look for that loose wire). I have no idea what the burp near 2 seconds is.