I currently own 2007 G35S, 2010 M35X and 2017 GSF. Maybe I don't drive faster than you but I do believe I don't drive slow and faster than most of drivers on the road. My 2000 Maxima had done 4 wheel drifting at 90km/h at high speed corner on city expressway in Taipei (That’s the only accident caused by me in my life, 30 year driving in Taiwan, USA & Canada. Luckily I didn’t impact any other drivers.). Before Maxima I drove Primera (P11, built in UK). When I changed to Maxima with OEM suspension, I felt soft and bored. After I replaced with Koni and H&R, I felt it’s even better than my previous Primera. Even though I own 2017 GSF now, I still think on mountain road (not on the track) my previous modified Maxima was quite good already. I have tested GT-R, M3, 86, etc. I think GT-R was most stiff car and it is even stiffer than my G35S with KW V3 or PSS10.
If your car’s unibody is not stiff enough, you can put strut bars and chassis braces to reduce the flex in it. I have put them on my G35S and they did reduce flex a little bit but not much.