SSSimon said...
There's also the steel cable reinforced key-lackable tie-down straps which will keep the honest people from stealing your board.
For all locking systems up to and probably including an amoured van, once the professional thief spots your board regularly, there is not much that will stop an 18V angle grinder.
Kanu Lock.... althouhg like SSSimon said, deters the readily drop kick thief, but if someone really wants you gear they will get it, I have both the Kanu locks and the SUP taxi. both have steel cable through the belts.