I've built a pair of Estes Fat Boys now & don't like the results I've gotten with both of them when only flying them on C6-5s. Both were built stock & have gone arrow straight on B6-4s but they have (IMO) rather dangerous arcing flights with C6-5s. There is no somersaulting, lawndarting, or anything extreme of that nature but I'm beginning to question its stability with anything bigger than a B6. Wind was calm the last 2 times I loaded them up with C6-5s however they began to arc quickly after leaving the rod (there was no movement in the rod leading me to say is is not rod whip) until they are parallel to the ground ~150-200ft off the ground. They both ejected & recovered safely (actually I lost the first one in some dense bushes) but I was a little nervous from the last flight because it headed in the direction of a nearby roadway (thankfully it fell _way_ short--it was the idea of seeing it head in the worst possible direction that scared me!) (In fact, I was pretty blown away when only minutes before I flew the second FB on a B6-4 that went _perfectly_ straight up so that I watched it come to a full stop with the NC pointed upward & it fell slightly backwards before ejection. Can you say NO WIND?!? That was soooo cool to see!) What I'm guessing is that it's a little too light in the nose. Anybody have a similar experience & care to share on what they did to resolve the issue? Thank you for your help!