bfw wouldnt work, as most trials freewheels are threaded so the lockring is self tightening. you put it on the back, the lockring will naturally unwind itself over time, and it'll explode. you'd need 22/18 gearing as well, and i doubt youd have enough clearance in most mod frames. mine was the same ratio 18/12, and it was only 48 click I think, it was a profile mini cassette hub. sounded nice though, but my tensile freewheel is loads better. I'm confident it's not gonna let go, where as the profile you were never quite sure.