I endorse those who advocate locating the rear wheels of the pickup vehicle in a ditch or gutter. 40 years ago I owned a Honda TN360 half ton micro truck, and I used to do either that -- or back-up to an earthern ramp. I had (still own) a heavy timber plank to which I had bolted a metal lip with angle to match the truck-bed lip (or really- tailgate).
As has been stated the sump clearance of the two-wheeler has to be watched as its mid-point passes over that lip.
There are two other options:
This features Tie-Down anchors to stabilize the two-wheeler as its brought to a halt at the top of the ramp. After securing the two-wheeler, the lower-end of the ramp is jacked-up higher ---- sometimes to make it level with the bed of the pickup. In any manner, this eliminates the sump clearance problem.
Problem here is that something else (or second lift) is required at destination. Using the lift, the two-wheeler is vertically raised to the bed height, and rolled aboard.
- Yet another way to secure a two-wheeler to pickup or trailer.
You just need to get the curved section up over the top of one tyre -- preferably the rear wheel. The front get butted up against a stop or front holder.