<<Have you figured out the target CP/CG for your rocket? You actually want the nose to be heavy and the tail to be light--the place to save weight is the fins, not the nose cone>>
Fins are 1/8 basswood, soaked in CA, very stiff, light (I've used thinner ones on Machbuster clones without a problem). Epoxy fillets add weight, unfortunately. I don't use Rocsim but am roughly eyeing the LOC Aura and THOY Robin as similar templates, although my fins in shape and placement are closer to the LOC Weasel (with relatively more span, however, as this roc is about 27" long). So I'm figuring the CP is about 18-19" from the nose. WRASP suggests optimal weight is around 8oz, and I'm at that with fillets and LOC cone before altimeter, chute/streamer, paint. I'll just shave weight where I can and go with whatever results. How far back from the nose/payload joint should the altimeter hole be? I'm thinking of getting that itty-bitty one from PerfectFlight.