Created LOC Warlock sim in OpenRocket, and got stability of about zero calibers with more or less any motor in it. Looking around, this kit shouldn't require any nose cone weight, right? What I have so far is: Total weight with recovery: 3kg (6.6 lbs) CP (OpenRocket estimate): 921mm (36.25") about same as location of front CR CG (no motor, measured): 865mm (34") I found a screenshot of one sim of Warlock that uses "base drag cone" to simulate base drag in RockSim. Does the OpenRocket takes into account base drag in its calculations already, or is the same trick needed in it?

I'm pretty sure it doesn't. I added about 1lb of weight to the nose of my Warlock, some will say it's too much, and maybe it is. Normal sim shows about .41 stability and model with base drag is just over 1. Flies very straight every time.

It's essentially to add that massless cone to simulate base drag. It will save you adding a lot of weight up front. Here is the theory/technique but you are probably already familiar. https://www.apogeerockets.com/education/downloads/Newsletter162.pdf

Adding the massless cone moves CP all the way down to 43". If it's to be trusted, should be more than sufficient without any nose cone weight.