CoyoteX shaved his Metro's head and advises against it (pinging).
See starting @ post 10 in this thread:
Dumb Idea of the Day(TM)?: removing a compression ring to mimic the XFi 1-ring piston
Possibly shaving less than he did is OK - he took 0.40 off. See
http://www.teamswift.net/viewtopic.p...it=shaved+head