I think you're seriously over-weighting the weapons.
If you look at the some of their parts, I would HARDLY rate the 110G over ANY F4U (much less the 109K-4, P-51D, any Jug, the N1K2, etc. etc. etc.) in terms of overall combat capability. It's a good gun platform and strike craft, and if someone isn't paying attention she can give you a nasty surprise, but the 110 is THOROUGHLY out-classed as an air-to-air combatant.
For that matter, the Tempest doesn't belong at the top of the list. She's fast, yes, but maneuverability is average at best and performance begins to drop off significantly with altitude. 1v1 and assuming equal pilots and starting positions the F4U-4 will win about 90% of engagements between the two unless the Tempest turns tail and runs away (which is usually what happens). Her gun package isn't as good, but the -4 just has better capability of getting her guns ON target. Doesn't matter if your guns are bigger if the other guy is the one who has the shot.