^^^ so why dont we have massive heavy flywheels if we "need all the kinetic energy transfer you can get".
If you are changing a clutch put a lighter one in, if you are not doing the clutch then leave it. Ligher flywheel will always be faster through the revs, I do not believe for a second that the revs drop so fast through the gears that it is an issue... besides, you have a ligher flywheel and the engine can overcome the interia to speed it back up again!