A number of people here use 303 Protectant. It's a non-silicone-based UV protector that you can find at places that sell kayaks and other outdoor gear. Maybe West Marine has it, too. It's good for all kinds of gear, like your PFD, spray skirt, etc. I've only used it on the vinyl parts inside my car.

The problem with silicone-based protectants is that if you want to re-varnish your boat, you have to make sure you get every last bit of the Armor-All (or whatever) off, otherwise the new varnish may not adhere well. I think the silicone stuff will only come off with solvents, and I think 303 comes off with soapy water.

But you already got all the UV protection you need with the varnish on the kayak. Take a break from building, go for a paddle, and coat yourself with water instead. Then think about building the next kayak...

Dean