I just can't trust the plastic-ness of rhino ramps.
Thinking I might build my own ramps out of wood as a project.
6 pieces of 2x12x120. Maybe Home Depot or whoever can cut them into the lengths I need. The GLK will have some work to do

Minimum tolerance seems to be 6 inches of clearance vs. 32 inches run, so about 10.6 degrees (front end of the Z4).
My ramp should get me 9 inches of lift within a 7.5 foot ramp length. About 7.3 degrees incline to the final step. Only rough measurements of the Z4 so need some extra margin.
Might build some 3" high ramps for the back wheels too. That way the fronts are up 9" and the backs up 3" (or vice versa), should be plenty of lift and no jacks required.