Does anyone know what size of rivets are needed to fix a gooseneck to a superspars M7 alloy mast.

Hello Garry
The normal rivits are 3/16 and made from Monel, they need to only go in to the mast wall by 3mm, if they are to long they will not pull up tight. If you go to a Chandlery you will pay a lot for a packet of 5! If drilling the old ones out only drill of the heads and punch the rest out, this will keep the hole the right size. Drill size for 3/16 rivits is 5mm.
PS This is with my Z Spar hat on!!

Agree with Craig. Measured mine this a.m. diameter is definitely 5mm. My gooseneck thickness in way of rivets is 4mm, I guess the mast wall is 3mm so rivets would need to be 10mm in length.
Peter

Very helpful - thanks.