[PorscheGAL]

Perhaps I am missing something, but you should have no problem working a 4 post lift with your garage floor.

Our garage floor slope is 6 degrees with a 10" difference between the front legs and back legs of our Rotary 4 post lift. We have no shims or special ramps and have no problem with pulling the cars onto the lift. (930, 911, lotus, etc). We do have an 8" concrete base and use plenty of wheel blocks when a car is on the lift.

I would be happy to provide pictures. Again maybe I am missing something from your write-up.