The stock tank is actually pretty well designed to keep the Center if Gravity low and toward the center of the bike, most especially when you are not running a full tank of gas. The lower the fuel level becomes the more the fuel weight is balanced lower and more centered.
When tracking my Porsche and using race fuel versus E85 I only run with about an 2/5ths of a tank of fuel to keep weight down, I would expect to use the same strategy with a bike for 20 minute track sessions, which would get the fuel CG pretty close to where the fuel sits in the GP bikes.
On another note on handling versus stability.
I have ThysenKrupp wheels and Sicom carbon ceramic rotors, 520 lightweight sprockets abs chain, abd am running a 15/44 tooth final drive setup….that’s somewhere around 12 to 15 pounds of lost rotating mass….which in turn eliminated ALOT of gyroscopic forces…this made the bike so light that you can flick it effortlessly side to side….but the higher final drive made it wheelie more, and the lower gyroscopic forces took away a lot of the stability it had, which wasn’t great already when pulling hard off a sweeper (something I do all the time even out on public roads) I rarely lean the bike more than about 45 degrees out tooling around, but I frequently do hard accelerations from 80 to 160 mph coming off of lean angels like that, and get the same wheelie problem but with less experience than you handling it haha.
The point is, I dialed SOOO much handling in via the super lightweight rotating masses that I can give some of it up for better stability and still have more handling ability than I have riding ability.
To that end I put on the IMA Triple clamps that have eccentrics that allow you to shorten or increase the trail without changing the rake. I added about 4 mm of trail and that dramatically improved front end stability that in combination with the super lightweight rotating masses and lower gyroscopic forces also kept REALLY good turn in characteristics even with improved stability.
I think with the extended swingarm matched with the right spring rates/sag/compression/rebound settings I can increase stability in the rear end without giving up much handling at all, and get at least SOME help with the Wheelie issue from my final drive ratios. The key will be getting the spring rate right along with the other suspension settings.
In short, I’m not nearly as experienced as you, but from my little bit of personal experience it seems like if your willing to spend the money you can increase both stability AND handling by making these geometry changes combined with super lightweight rotating assemblies that reduce gyroscopic forces.
