Mine has flown and there was no stability issues. You need to extend the engine mount tube down to the bottom of the fin unit. You will also need to cut off the main body tube a piece equal to the length of the fin unit. One thing I would recommend though from my first flight with it at NSL in SC. It flew fine but the booster chute did not open too good so it hit rather hard on the ground that was almost like concrete. The impact broke all the little, discrete struts and it now wobbles on the body. I would recommend putting a tight coupler tube inside the fin unit between the two sections so that if it hits hard it has something to prevent damage. I am going to have to remove the aft section at that joint, put some small plastic rods in to replace the broken ones, and put in a coupler tube.