I launch from the bed of my truck, but it's not lifted. I back it in until the end of the tailgate is touching the water (about 1/3 to 2/3 up the rear wheels depending on the ramp grade).
The diff breather runs up to the frame so it stays out of the water.
Never had any wheel spin upon exit, one of the ramps I visit is covered in sand at the bottom and the other is roughed concrete with deep horizontal lines.
I also set the e-brake and get out to launch the ski, I wonder if I should be reconsidering that... It never moves even an inch though. The parking brake has shoes inside the rear rotor.