I am using Rupes LHR21 + 5" Backing Plate and MF Pads and cutting polish like Menz 400 / MG #101 / MG #100. More powerful than the Flex 3401.
No problems on tighter curves. Just a matter of technique. For really small parts I use my LHR75 (side skirts, bumpers, wings...)
Rupes LHR21 + Optimum...