After finally getting the right rivets for the job, I started to re-rivet my mast base today. I was pretty surprised to see how corroded the base was when I got it off (I'm going to try and attach a picture of it).

Can anyone tell me which rivets are the original Hobie rivets? I know they only put three in, but the previous owner drilled two extra on each side. On the mast itself, hole closest to the sail track on each side and the hole in the front of the mast are still in good shape. I suspect these are the original 3 rivet sites. When my replacement base arrives I'm thinking of just replacing the original three rivets and just making sure there is a good seal around the 4 extra holes in the mast. Any suggestions?

I'm also curious to know what the "plug" inside the bottom of the mast is made of. Is this something that is easily replaceable if I need to cut off the very bottom of the mast to start fresh with the rivets?