Update....what a difference an empty tank makes...lol. I took your set up Nissman, which was already pretty close to mine and started running a few laps and then I thought, what the heck, I'll just keep going and see what difference the fuel load makes. So every so many laps I'd change tires but not fill up the tank and the times dropped fairly consistently maybe 4-5/10ths with each set of fresh tires and the handling improved. I was able to go flat out eventually from the last left hard left hander, through the esses all the way to the 2nd/3rd gear left hander in the tunnel.
Eventually I got down to a 1:16.5, on Trial Mountain, which I didn't think was possible for me, but the big difference I think, was the fuel load. I did start to take some slightly different lines, with slightly later turn in's and later apex's and it did help shave off a tenth or two here or there. I also started dropping to second gear in the right hander before the last two corners, for just a second and found it brought the nose around quicker and allowed earlier power on.
I know I expressed some doubts, but I pursued this with the goal in mind that those times were possible with my DFGT wheel which is why I've probably run 150laps to find this speed. I have to say thanks to you Nissman, not just for the tune , but for making this post and giving me the laps times because it motivated me to put some effort into finding that speed and I'm a much better driver for it. I've still got a long ways to go...lol.