Rivet caps are thin metal top-hat-looking sleeves (condoms?) that you slip around the rivet and into the hole before you pull the rivet... they waterproof the rivet with no caulk/gunk required. You'll need a burly rivet gun to pull these stainless-steel rivets. I bought a Harbor Freight air rivet gun for mine, but I'm a tool-slut... I'll never have too many tools.
Matt posted up the comp tip installation instructions in another thread:
https://www.hobie.com/forums/viewtopic.php?f=23&t=58920 Time flies when you're reassembling... and the pot life of your adhesive can complicate things. Definitely do a dry run on assembly before you mix up the epoxy. Inserting the comp tip, aligning the stainless hound tang, inserting rivet caps, inserting rivets... get a feel for that before you mix adhesive. I had extra entertainment doing this all signle-handed and working against pot life... all the aforementioned assembly plus pulling the rivets (then picking up the rivets that drop out when you 'pop' the other rivets, and reinserting them), pulling rivets (curse/pickup/insert/pop, curse/pickup/insert/pop, etc.)... a second pair of hands would have been handy.
You might also want to add some thickener to the G-Flex, depending on which version you got, it runs pretty thin when it heats up to cure... I've had some run enough to leave me concerned that the joint was fully wetted.
Randii
p.s. If I recall correctly, you're in the foothills area... you could borrow said rivet gun if you'd like, assuming you have an air compressor with which to power it.