I ran some estimates of paint weight vs new stability numbers, and I'm not sure I'm using the program correctly. I've been using Barrowman numbers for stability - I was under the impression that they were more conservative. Though this may be an error as the design is nowhere near typical.

Baseline rocket with engine but without paint: 5.744 oz, 1.67 stability (Barrowman). Center of gravity is 16.025" from the front of the rocket. I estimated the added weight of paint to be 1.06 oz (rocket without engine is 4.24oz and I assumed 25% extra weight (1.06oz). Total weight of rocket with engine and paint should be 6.8 oz. I put that in the Mass override and enabled it, and now the rocket is stability 8.74 (overstable). I imagine that I should also override the center of gravity, setting that to be 16.025 (the original CG before adding paint weight)? If I do that, then the stability drops to .74 (marginal).

If I switch to Rocksim stability equations, then stability is 2.13 w/o paint, and 1.2 with paint, assuming the CG is forced to be the same as it was originally.

Am I doing this correctly? I wanted to get things sorted out before I built the rocket.

Picture of the rocket in question: