The problem I have found with all my attempts at locking up kayaks is that a good pair of bolt cutters will go through just about any cable you could lock it down with. I always wanted to try a Club (used for locking steering wheels) across the coaming, not sure if it is big enough though. That would foil people using the boat. One thing I do is keep the hatch covers locked up seperately. Having no hatch covers will make it real hard to use/sell these boats. Hopefully the would be thief will realize it too....