Greyfox, I used a Zenoah G-20, which IIRC weighs about 42oz. I moved all servos to the wing bay making two sided servo mounts for the elevators and inverting those servos positioning them to the bottom and aft of wing bay. The rudder servo is forward and upright (looking in the bay) using a servo box cut from the engine bay. The throttle servo is also inverted. I used a manual choke rod that exits the cowl along the side of the fuselage between the fuselage and the cowl. A short 90 deg bend on the end servers as the grasp point.

Other items beside the triangle stock you mentioned are I filled the gap under the wing bolts. After a mishap repair, I put a nyrod jacket through the wing mounting screw locations, cutting the inside out by making a saw by filing teeth on a wing tube section and a multi tool to cut the nyrod to the surface of the wings after masking the area. This combined with using a screw in the center of the middle wing section to lock the tube in place makes mounting the wings much easier. To do that, I simply drilled from the top of the center wing (area that would be inside the wing bay) and then tapped the wing tube for a screw. This worked well for me because I leave the tube in and use it to store the plane.

It flies very good with almost all of the challenge involved with landing. I used the struts, which are angled well forward and would recommend the retracts only for a hard surface or very short smooth grass due to keeping it on its feet. I had one mishap when letting it get too slow on landing... it stalled... dropped a wing.... it caught and cartwheeled. Fortunately the damage was fairly light. I chronicle that repair in the crash forum.

Power wise you will of course be fine with the 26cc. Mine required moving the servos to the wing bay to balance but that might be in part because I wouldn't spend the high dollars on a spinner and chose instead a solid prop nut that weighs nearly 4 oz ( I have a metal lathe). I also added dowels in front of the dummy engine to simulate push rods and they added some forward weight. These were spray painted silver and IMO worth the effort and give the front end a nice look.

The last time it flew, we had little wind and I can still recall thinking about how great it tracked.