I've used these before, but not on a kayak.
The rubber is soft. I used them for running open wiring on a multi-motor machine. They're good for running tubing, and might even work under the deck, pump hose...

On the deck I think they'd be damaged by saltwater, sun and abrasion. Also they'd stick up too high for practical use on a kayak deck.

One thing I never knew about stainless steel is that it needs oxygen. It needs to be exposed to the air or to water or it will corrode. (These clips would be OK on the deck, but I think the rubber would dry out, crack and get knocked off.) Bronze gets a nice green patina and then it's good until archeologists dig it up. I'm probably going through a bronze age, I look for bronze whenever I can.

Deck line connectors that screw into the surface, stick up too high, the screws don't have enough to bite into in a kayak deck (1/4" soft wood, two layers of glass and epoxy)

I'll use the surfboard lead cups discussed here on my current kayak project.

made by Ancor.
: http://www.marinco.com/product/stainless-steel-cushion-clamps
: As you can see on the website, they come in a whole range of sizes.
: I got the 1/2 inch, which look strong enough without being
: over-sized or overly heavy. Does anyone have experience using
: these?