A long time ago, I repurposed my dads old/unused boat trailer, and made it into a trailer for my dirt bike. It was a simple trailer, centerbeam + wheels/axle on a triangle frame. I moved the triangle frame forward a couple feet, shortened the centerbeam, kept the bow brace/winch support for a front wheel chock, added 2 eye bolts for the ratchet straps. The centerbeam was the right width and had a ridges to center the keel which also made a good tire channel.
That trailer served me very well for 10 years, hauling my dirtbike around the state. I rescued my pals bikes a few times. Loaned to my pals dad who took it to Colorado several times with his CB500 aboard.
My 750 never went on, I didn’t have a ramp. I could lift the dirtbike and load it by myself. I’m certain I couldn’t put my 750 on under any circumstances, but I never needed to.
I have been contemplating that a jet ski trailer might be reworked into a motorcycle trailer.