Erich,
I also use 1/4 in. cord through plastic pad eyes and attached at each end with a plastic bundie clasp. This way the cord could be removed during a trip should you require another use for it or for an emergency. As for deck mount compasses they are commercially produced for just what you are asking (similar to deck mount bags which attach to deck pad eyes). You might want to investigate dimensions and then make sure you have pad eyes located in the right area of your deck to attach the compass.

: We are at the final stage in finishing our kayaks and need some advice. What
: size of bungee cord is the most common on a kayak? We have the 3/16 and
: 1/4 cord and would like to know if there is a preference for one over the
: other. One has more holding power than the other but is that really
: required? And are there any pictures or plans available for a compass
: mount that has bungee cords to attach to the kayak. I am looking for one
: that looks like a spider and has four legs that holds the compass on top
: and is easily removed for storage. Regards, Erich.