TAF advice on rivets

TAF have advised that I should switch to a flat nosed rivet gun for subsequent rivetting, to ensure better sealing between the head and the aluminium surface.

They advised that their factory rivet guns are supplied with dished nose-pieces, but are ground flat.

I contacted Toolfix, local distributor of Gesipa rivets and tools, and confirmed that their own rivet guns also have a flat nose-piece.

It is increasingly clear that the Gesipa rivets should be set with a flat nose-piece, period.

I am weighing up what to do about all the existing rivets that I have set.