I just put solder in the allen keys I'm bothered about - so seatpost bolt and stem bolt. Torx would be easier when it came to adjusting/taking apart though.
I had been thinking about swapping out all the standard allen bolts on my fixed (as it is the only one that gets locked up) for Torx to make it that little bit more difficult for Jimmy McScum to make off with important parts.
I just put solder in the allen keys I'm bothered about - so seatpost bolt and stem bolt. Torx would be easier when it came to adjusting/taking apart though.
Or even better:
http://www.securityfasteners.net/index.html