My 15 hand, very stocky (read:fat) QH mare loved to jump. She has been retired from it already (she's only 8), since a bout with cellulitis damaged the tissues in her leg enough that the vet recommended a less demanding occupation for her. She was leased to me last year, and has been a very healthy, fairly sound trail horse. Any lameness was from stone bruises or a fall. However, before her illness, she was jumping three feet pretty regularly. Even now, if I ride her past a jump, she tries to take me to it. She loved to jump. On the trails, given an excuse, she'll jump anything. Heart and desire will go far in overcoming physical limitations. Just be sure your horses are fit enough for what you ask.