I have arthritis in my knees and when I first got the MH my knees would throb after 1/2 hr ride. There is an extended point at which my knees feel better but my slide in back of the chair prevented that. So I sat in my car and measured the knee angle with a protractor and duplicated that angle in the MH by raising the seat up which helped immensely. I used a block of oak and longer grade 8 bolts to fasten the seat back down. I also used a 4 x 4 in block of oak to place my heel on just before the gas pedal further extending my knee in a more comfortable position. I can now drive about 3-4 hrs before the throbbing sets in. My second mod is that I always wear shorts so I can rub on Bio freeze or another arthritic rub before the pain gets too bad. My third trick which my wife hates is when I fully extend my leg and rest it on the doghouse for a few mins. I like the lower dog house of the WH chassis for that reason.