Some 3m 5200 mixed in with copper rivet nails. (AWESOME write up on the riveting process in Wooden Boat copy #191!)
I.M.H.O I believe is the best thing to do. Epoxy will certainly crack due to not enough flex additives,(tried that once on the bay head skiff!!!
Riveting is a seperate issue than caulking. Caulking of any kind does not keep any kind of boat from flexing or evening opening up. On solid and aged woods all you are doing is causing unncessary grief down the road. Boats move and flex because of two reasons. The interior structure is inferior or aged with fatigued fasteners if applicable. There are those in the business that recommend 5200 which only creates nightmares down the road, especially in aged hull thats redone unless you rehab the entire boat hardwareand or investigate the soundness of its framing too. Sea skiffs built with solid timber reacts entirely different than boats built using plywood for the planking. Painting 5200 with anything is next to impossible and using two part paints which many people do here on it is a waste of energy and money too.
The use of rivets is favorable for the solid wood applications because of the need to move and an age old practice proven to stand the test of time when plywood was so "in the future substance". But those years also prescribed to oak and hardwood framing and interior parts that combined together to make the boat one unit. When planks fatigued, replacement was the order of the day for the proper craftsmen.
Of course folks patched and puttied and got by but rarely did they not understand the increased maintaince for leaky boats and suspect woods. Many of the bigger boats were also stored in the water which also kept things together. This is a plus too to keep boat parts and movement of boats in good condition to a minimum too. One of the reasons why cotton and oakum was used with such success was to allow for the seasonal changes that occurred in all traditional boats. For some reason people recommend the use of 5200 type caulking for wooden boat seams to fix huge seam cracks only to literally destroy the boat when it hits the water from being stored on the hard.
Rivets are not needed and really not even recommended on lapstrake hulls when you also use epoxy. All it does cause is an uneven surface on both the inside and out in which to paint and refinish around.