My 4*60 was significantly tail heavy also and with a Saito 80 I just kept adding and adding lead. It flew fine but obviously lighter is better. I added two 1/2" square formers behind the engine amount as spacers pushing the engine mount that far out and changed to an OS91. I was able to remove about half the weight so now I think it's lighter even though the engine is a little heavier. I have warned a couple of friends building this plane to monitor very carefully the glue in the fuselage to try and keep the tail light. If I was to build another I might even try some tricks such as putting holes in the tail surfaces etc. Your's should fly fine, the wing is plenty big and even with the extra weight you should have no problems.