Thom,

You may not be dealing with unsophisticated thieves, you just may have
gotten lucky. Even if they were unsophisticated, if they are 
persistent, then you will be in for a long period of attempted
breakins.

I would say that the club may be a temporary solution, because
eventually someone will show up with a hacksaw or bolt cutters.

I'm just wondering if one were to get a 4" length of 2" dia.
pipe, slice it in half so you have 2 4" semi-circles. Next weld
in a hinge on one side and a lock hasp on the other. This "collar"
would then be put onto the arm of the brake or clutch pedal, thereby
rendering them inoperable.

Just a thought...

Ric