Robin may have a good idea about using stronger monel rivets - I'd add
just a note of caution that the original aluminum ones may have been
selected purposely by Amel such that in the event of a malfunction they
would break sacrificially before ripping the metal of the roller
extrusion. I don't know that for a fact, but it's plausible.
Also, while Monel itself is corrosion resistant, I don't know if there
would be an issue with it being in close contact with aluminium.
Perhaps the most conservative approach would be to stick with the
material Amel originally used - my Aluminum replacements are 5 years
old and are in perfect condition (I now inspect them regularly!!)