In CGs, or festivals, security is good enough, and thieves tend to go elsewhere.
Storage yards are where the break-ins happen. There, it really doesn't matter what lock you use, a "master key" (long screwdriver) will get in. Doors, there are many ways to get in, be it lifting or smashing a window, or whatnot.
My recommendations:
1: Replace the CH751 locks with triangular cam locks. The "key" is uncommon enough so that not people will have it, and will provide good enough security, and not get fouled with road grime. If one wants a real lock, Check Amazon for some that have a shutter.
2: Rekey the doors. FIC sells the cylinders, but to get the tool that allows you to pull them, you may have to hit eBay.
3: Insure and store valuables out of sight. Keeping a database with pictures, serial numbers, and other things will be a great help if there is a theft.