Well I'm going to have to eat some crow here and state you're right... I DID take into account many different factors, and I wasn't just saying it without considering it. I was going off an understanding that HTCs charts had been verified with in-game testing. However, I'll explain where I went wrong for my own defense.
2 things. First, HTC has misleading charts. Their new charts CLEARLY use 100% internal fuel (otherwise P-47N climb rates would look different compared to other P-47s). Second, I used Gonzo's charts assuming they were independently verified/tested in-game. There are certain quirks/bugs/kinks in Gonzo's charts where they do not exist on HTCs. I took this as recording errors when taking notes. So, turns out they're just copied from HTC apparently.
9682lbs is exactly the weight of a 190a8 with 4 20mm guns and full internal ammo.
However, HTC just copied and pasted the chart and weight for the F8, assuming (justified or not) that at that same loadout the F8 would be identical. However this is not a valid comparison nor is it accurate. It's just presenting bad info. There is no configuration for the F8 that I know of that gives it 9682 lbs. If you drain the AUX tank down but leave FWD and AFT full you get 9667 lbs. However there is no fuel setting for this -- it would be about 80%-85%(?) internal fuel (between 75%-100%). [EDIT: If you shoot off all your MG ammo you get 9678, shaving 171 lbs off the 100% "stock" configuration]
I had really thought HTC updated that info when they redid the charts, and the Gonzo charts page to me confirmed their validity. Shows me that I can't trust the basic info that HTC puts out about their own planes. I really wish the would update these wrong charts. Use a similar setting, whatever that is (50% internal fuel baseline, standard weapons, clean configuration, whatever -- just be CONSISTENT). It would be infinitely more helpful to have real numbers instead of "Use those numbers, just keep the weight the same".
It would also prevent major blunders like mine, here. Might be worth the time and effort updating the charts to avoid that kind of headache on all parties involved.