Jimmy, maybe you've set up your Skyline well, but the RX7 not so well..? Just done some testing of my own at Autumn Ring, all of these set up to handle well - rear end not stepping out, quite happy with all of them. Maybe the S2000 could be improved but not much, few tenths maybe. I did 3 laps in each car - I can get to my fastest pace quite quickly, here's my best times - draw your own conclusions imo...
RX7 Spirit R: 1:18.980
370GT: 1:20.317
RX8: 1:20.321
S2000: 1:20.578
When I did the same test at Nurburgring GP/D there was a much bigger gap - 3 seconds - between the RX7 and other cars.
I think myself and Jimmy are probably about equal in terms of pace, so I'm not surprised he can do 1:20.2xx in the 370GT, I probably can do that too if I get a near-perfect lap. That car despite its weight seems to have a lot of mechanical grip and good acceleration too, so actually quite competitive (surprised tbh).