I built one with a Brison 3.2 with a Slimline Pitts muffler. I had to cut out a fairly large portion of the firewall at a 45 deg angle to clear the chamber on the muffler. I would think it would be worse with a G62 being a slightly larger engine. The biggest problem though is the fuselage is very narrow compared to extras, caps, edges, etc. I had a tough time mounting two tanks, smoke pump, ignition module, ign battery etc. If you still have the magneto ignition that should help a little with the mounting of the components (or lack of) The cowl is also narrow, The muffler sticks out slightly on the left side, where the wrap around is to connect to the exhaust port. It doesn' t look bad, its almost flush with the cowl, but I had to cut it out to prevent chaffing, so you can see the side of the muffler with the smoke tap and tubing. I also made a hatch behind the firewall on the bottom of the fuse to access the ignition module and battery. Its a strangely shaped hatch due to all the cutting on the firewall, but it came out pretty good. Mine weighs 19.5 lbs.

Brian