Hey guys I have been thinking about upgrading to a Ultrex. I have a 618 with a 175 Pro XS. I currently have a 80 pound Fortrex, There is plenty of room for another battery if I decided to go with a 36vt Ultrex but I would have to upgrade my charger as well. I guess my question is would I lose much performance if I went to the 36vt? and has anyone ran a 24vt Ultrex?