He has a bergman 600 and loves his csc trike so he wants to think about selling scooter and modifying trike thanksIf he can afford a new wing the DCT maybe the answer. Or a large scooter. I had a 600cc Honda Silverwing for a while. Very quick and a smooth ride. Lots lighter than Goldwing, just not as much wind protection or storage space. I don't think it had linked brakes however. So that might be a deal breaker since the rear brake is where the clutch lever would be.
Good luck with your search.