Should have known better than to post without doing a search. Found my answer in this thread
Welcome to the Spyderco forum.
The question is far more complicated than you might think. If we put it on the spine of the handle, it will block the lock and unlockinbg would be difficult.
Would the spike lock? what type of lock?
Our "tusk" design was quite nice, and very well received but our H1 maker couldn't make it.
We would like to add one to the line, but design and engineering to do it properly, is time consuming. It is on the back burner, and we thank you for your request.
FWIW, Eric and I are both sailors, so we understand.
Perhaps the design could be simplified.
You are into a realm that is delegated to me......sailing. So it becomes my job to respond.
The "Tusk" design used a linerlock for the blade and a ball bearing lock for the spike. Eric's design. Shackle key is built into the form.
I can see how the use of two different locks would make the engineering complicated (and expensive). What about using two RILs like the Dyad prototype or the AGRussell 'Seamaster'? Make the shackle key a slot in the handle. Use a fairly narrow blade like the Mariner so that it works better as a rescue knife
Just my AU$0.02 for what it's worth (not much these days