Problem With Pop Rivets On A Mast

A friend of mine is up from Bocas and is working on replacing a steel sail track on his aluminum mast that has a total material thickness of track and mast of 1/4".

He wants to use pop rivets to avoid drilling and tapping 200 holes.

1. Which kind of rivet material should he use: monel or steel or other?

2. For the 1/4" thickness of the material he is trying to use 3/16" diameter rivets, in that case which length rivets would be best to try?

Any other suggestions?

The boat is a Morgan 462. He wants to continue using the Harken steel track because of its strength. He uses double stick tape to hold the track and provide a barrier/bedding layer. He then uses tefgel on the rivets to provide a barrier between the steel and aluminum.