OK, I have found my first dislike of the G4. The 1st gear ratio is with stock gears is 6.42 which is waaaay too big for the little tracks where run on around here. One of the local tracks is a bunch of sharp turns and you need to be able to accelerate hard to get to the next turn. The best I will be able to with a 19t pinion and 52t spur is 6.89.
I don't know what your motor/clutch set-up is, but I can tell you my G4 easily pulls the lower gear (numerically) no problem at all.
When driven back to back with my Flex (7.71 / 6.10), The G4 (6.32 / 4.85) easily pulled as hard as the Flex. It almost seems as though the gearing is NOT that far apart, but on paper is surely is. The light weight of the G4 (a couple hundred grams lighter than my Flex) and the lighter rotating mass must really work because the I was stunned how hard the car accelerated. In fact the box stock G4 reset our local track record which was half a second better than the best lap I ever put in with my Flex.
Oh and I think your estimate of 6.89 is wrong. I believe the best you an do is 6.78. I have calculated the internal ratio as 2.48 where the Flex is 2.52. Does anyone know for sure if the G4 is 2.48 internal?