Rutgerson stoppers

[HappyAfloat]

So I show you my progress today.

This is like a trip down memory lane 

[Ailatan]

After a little bit of gelcoat now the base is ready for the new set of stoppers. According with the drill guide I should use M8 CSK fasteners but I don't know which type of head I should use. Does anyone know with which head you can apply more torque: Slotted, Phillips, Allen, Torx...? I don't think I need the torque now to install the clutches but I can need it in the future to remove them.

[Yngmar]

Torx or Allen. But if you just put a little waterproof grease on the threads (silicone grease is great), the bolts won't let water seep past, avoiding corrosion and seizing up and will still come out easily in decades.

[Ailatan]

After two months waiting (importing goods from UK is crazy is much faster from China) the clutches finally arrived.
I chose the Spinlock because I wanted a clutch made out of metal. That shorten the list two brands Antal and Spinlock, but Antal had the holes very similar to Rutgerson and I preferred the longest distance with the old holes.
I already made the holes and the thread in the aluminium plate but appart from the silicon grease in the thread of the screws recommended for Yngmar I don't know if I should use silicon or butyl. Anyone with experience? Pros and cons of both options?