Volfy, Your right about the wheels they are heavy. I sold mine here on RCUniverse and used a pair of Dubro 4.5" Treaded Lite wheels with the grey hub. They fit perfect and are the scale size and both wheels are lighter than one of the factory wheels.
I ran my engine again last night to check for radio interference and was getting 7650 out of the 16x8. Did the new ring or the CH ignition make the difference for you? Or both? To keep the weight down we put all servos in the tail and a 1800 mah, 5 sub c cell battery pack in from the bottom below the servos. I got the measurements for where to put the servos off from one of my Modelsport videos that featured this plane. We built a removable plate on the bottom of the fuse below the servos and attatched the battery pack to it. When installed the battery just clears the servos. The plane required no other weight to balance this way. Yours might be different being as you ditched the flywheel. Ours weighs exactly 14lbs. The pilot figures are very scale. They have oxygen tubes and a .45 in a holster and everything. Very realistic. When I paint mine I'll send you a photo. For those interested Paul said he would install the molded struts that are mentioned above and shown on my plane to your factory gear legs for $20 returned shipping included as well as alter the factory cowl to clear the flywheel for $25. Later, Maximus