The difference is NOT small. In order for TOD to historically correct, you cannot have the P-38J in October 1944, nor in November, or in any real numbers even in December. The difference in performance is significant. The G is enough slower than the H in speed, acceleration, and climb as to be serious handicap to the 8th AF pilots in the 20th and 55th groups.
Also, the J is too good for it to be fair to bring it in earlier than it was. In fact, we have a J-15, which wasn't available until at least March.
The P-38 pilots shouldn't have to settle for a G when they should have an H, and the Luftwaffe pilots shouldn't have to face a J when they should be fighting the H.
It isn't JUST the P-38 or even JUST the Allied side that concerns me. It's getting the match up just as it should be.
There would be NO changes required to aerodynamic modeling for the H to be introduced, and only a very minor adjustment in weight, if any. The only REAL change would be power. It is not as though it would require completely creating a new model. The P-38 is a fairly recent update, so not much would need to be changed to make it correct.
I would certainly propose and support doing whatever is necessary to get the Axis planes correct as well. There are others who are working on the Axis part of it, and they know more about those planes than I do.
I KNOW P-38 pilots who flew this part of the war, getting it as right as it can possibly be is EXTREMELY important to me. I want to fly the H just as they did, and face the same Axis planes they did. That is VERY important to the immersion factor that makes TOD what it is.