Carrying a 500 lb motorcycle on the back of a Solitude 5er

Look into swivel wheel trailers.

They are a gray area in terms of double towing as the can't jack knife. The advantage is they cut the weight on the back of the trailer by roughly half.

The big thing to check is what is your current pin weight. You should be north of 20% of the trailer on the trucks pin and putting 600-700lb off the back will take several hundred pounds off the pin.