re caulking of stanchion base
I work in automotive and have dealt with my share of seized fasteners. Which bolt head type is "best" is an age-old question and one that does not really seem to have a definitive, scientific answer. Here's a pretty good run-down of most of the available options: https://www.wiha.com/en/screw-head-types/
In reality, the four head types that you can find relatively easy in 316 Stainless Steel in the sizes we would use on an Amel are:
1. Slot Head
2. Phillips Head
3. Socket Head/Allen Head (internal hex)
4. Hex Head (external hex)
In my experience, Slot Head is by far the worst choice in terms of both the amount of torque you can apply and in keeping the tool on the fastener head. However, it is available in the most sizes/lengths and is usually the cheapest option.
Phillips Head will let you apply the most torque to the screw head. However, you have to be able to apply a good bit of axial force (pushing the screwdriver down into the screw head) in order to avoid the screwdriver slipping out.
Socket Head/Allen Head/Hex Head is a good choice when you have limited access to the screw head and you can't apply a lot of axial force. However, you cannot apply a lot of torque to the head before stripping it out. Socket Head/Allen head are "prettier" and come in a flat head version which can sit flush in countersunk holes like the ones in the SM stanchion bases that we are talking about in this thread.
www.mcmaster.com and www.grainger.com are two good places to find 316 Stainless Steel fasteners in the USA.
SM 440 Cara
Deale, MD USA