I am going to still be running gears with it. So I will get a trials 6 speed hub and a mixed up cassete with gears from about 12, up to 22 teeth I think. Do I need a front freewheel for this or a cog? Does it engage in the rear? Also, what is the best out of the way trials derraiulerr (spelling)? Anybody know the wheelbase of an STP?