I think it's time to retire my 21 year old Mongoose mountain bike and get into something else. I would like to buy used because I can't see myself making a hobby out of this pedal machine, that being said, my wife is after me to bike more with her and the kids and I have a really good mountain bike trail right next to my house that I would like to wreck on. I would like to get a bike with a good frame that I can upgrade myself (I'm weird like that) but I don't know what to look for. The biggest problem is sizing, I am 6'4" and weigh 230 and it seems every dang bike manufacturer makes up their own rules for size. Any suggestion or hints is appreciated.