you can mate, i used to do it all the time....won't get the cover off with the reg on.....
wind the reg adjuster fully anticlockwise, then keep going....
you may then need to use a bit of force to get the reg adjuster to turn clockwise again....but ti works - lost track of how often i've done this servicing folks regs.....the trick is not to put it on over tight in the first place...