i have a 2004 trek 4300 that i have been riding on and off since i bought it new. the frame fit me when i was 13 and about 7" shorter , but while i have grown over the years the bike has not so i have come to get used to the small size i guess. so much so that when riding a large as per the shop's rec, the bike feels big and cumbersome.

i am looking to get more serious into the sport and feel that im a bit limited with the bike's setup. before i upgrade to a new frame or maybe even dual susp i want to have something i can beat the **** out of. so i was thinking of upgrading the 70 mm stock fork

isit possible to go to longer travel or would this mess up the geometries and angles making it unridable? i was thinking a decent air fork with 80-100mm of travel. would it work?