RE: Building a P82 with YS60's
As long as each engine is "happy", you won't notice a difference of 700RPM in the air. The biggest mistake people make with twins is to "match" the two engines RPM's. Ultimately when doing so, they're making one engine less reliable.....and when that engine dies they'll have a much bigger RPM difference. If you adjust each engine so it's running well, ignoring the other, you'll be fine. It's also very possible that the two engines will be running closer together once they're in the air and unloaded. Ground RPM is about as important to a flying airplane as the air above it or runway behind it.