Bike polo mechanics & fixing

@Jimmy - I think I can acheive the same effect by clamping the stam to the shim and wriggling them down together, I'll play around with this.

@ Chris? - I think HTFU is probably right. I've retensioned it at least once, but will carry on playing about and see if I can get it to settle.

Try using some threadlock perhaps, should stop the screws working loose over time.