I have two CMP arfs flying currently. A 50 size P-47 and 50 size P-51. Both have YS 91's and balance just ahead of the spar. They fly well with the 91's in them. My issue that I have had while building the P-47 was with the paint on the wing and rear stab. The paint jumps off the wing if you even look at it the wrong way. I ended up sanding down the wing and repainting the entire plane. For the P-51 I took a heat gun to the covered pieces prior to assembly. Once the covering was tightened up I went ahead and sprayed all of the covered and painted pieces with top flight flat clear. I've put 15-20 flights on the Mustang and the finish seems to be holding up pretty well. Both planes fly very well with my set up. I have looked at the websites for the suppliers and only have one question.............. spare parts? Cowls, Canopies, etc. it would be nice if you carried some of these replacement parts on the websites. Thanks.