I too am building a Super Skybolt, one of the two I have. I'm going to use an OS 120 pumper in it. Note that the plans specify that the thrust washer should be 6 1/16" from the firewall and should have an isolation mount. I have an OS mount however if used it would place the thrust waser at 5 3/4". I took a chance and bought a set of wheel pants from Tower for there ARF Skybolt, they are glass, assembled and painted AND they are the same size and shape. Iv'e made a mold for the cowling and have pullled one part from it so far. Man I detest ABS.