Well I have had to revisit what I do. I just made a 6 inch fat boy, and printed the fins. 9.5 mm thick, 4 perimeters, 30% cubic infill, ASA. Launched on a J350 and the flight was great. In retrospect, I used too small of a chute (it was the largest I had). The rocket was heavy and came down fast enough to bounce off the sod several feet back into the air. Cracked one fin, and basically broke it from the the body/motor tubes. Easily fixed (and in the future I need a much larger chute).
I already printed all the parts for a 6 inch big daddy as well. Same settings. So I am tempted to do a tip to tip fiberglass layup over the fins (has saved me with some other large finned fat rockets when landings weren't ideal). I am not sure if I could have changed much to make the landing survivable, when I saw it bounce that high I knew something was going to break. Maybe I should increase to 50% infill. Not sure if trying CF of GF filament would help with this either. I am going to print John's Nike smoke as an excuse to use an I65, so I have an opportunity to reconsider my settings for that.
