There are a lot of moving parts when a semi-automtic pistol fires: bullet, barrel, slide, hammer, the entire pistol and the shooter's hand and mass in not the only thing effecting the subjective "feel", there are also spring constants, coefficients of friction, heat, light, sound, and plenty others I'm not thinking of, so I don't think you can simply plug two numbers into an equation and call the problem solved.
CHA-LEE put a lot of time and energy into a very informative thread of slide lightening:
I've done lots of testing of my own and found results consistent with Charlie's. My first lightened slide had all the weight (1.8oz) taken from the front and I felt it increased the muzzle flip, I now take equal weight from the front and rear which gives much better results, I'm also a big fan of increasing stroke.