I've been trying to figure out what I want to do for securing the static lines to the bulkheads and longerons. After thinking about it some, I thought one of these wire tie bases might be a good choice. This one was borrowed from work and would normally take a #4 screw.

A CS4-4 countersunk pop rivet seems to fit reasonably well. I cut the base in half to check if the countersink angle matches that of the pop rivet...it doesn't. Not sure if that matters, but for now I'm keeping my eyes open for a better solution.