I probably shouldn't do this as I am sure to get something wrong and get womped for it, but here goes. Yes CG is center of gravity. CP is center of pressure. The best understanding of this I could give (and I am probably wrong) is if you imagine your rocket being of uniform density, what point would it pivot on if balanced and a wind hit it sideways. (Where would the pole be in the weathervane?) If the CG is one caliber (Diameter of you airframe) forward of your CP, your rocket will fly stable. As the distance between those two points grows, you rocket will tend to weathercock more. So generally clustering BP rockets becomes problematic as you keep adding weight to the rear end requiring more weight up front (in some form) to keep that CG in front of the CP.Care to explain? Im still not completely sure what exactly it all means. Im assuming its center of gravity. Nose cone is sealed off so i cant add any weight to it, but for a bulkhead a used a big round block of balsa that weighed like 50 grams instead of just capping a coupler so i hope that added plenty of weight. For shock cord ive got 1/2" x 92" estes pro series. Ive never used a chord this big, is it suppost to be that long or should i shorten it up?