I have not. I just hold my front wheels up until the rear wheels are about to crest the ramp and then sit the front down. I am only working with a 32" though, not sure how much heavier a bigger mower is to keep up on rear wheels going up.
2004 Dodge Ram 1500 4x4
2000 Toro Proline 32"
2011Toro self propelled
2003 Big Tex 70-PI 6.5'x16' trailer
Happy homeowner trimmer (for now)