Which liquid metal

[PaulRainbow]

I hadn't thought about heat causing issues with hardening. I've got some big boy filler which is the same as the op mentioned. Basically grp filler with aluminium filings in it. I will give it a go.

Is it waterproof ? If not don't use it or you create another maintenance job. Don't weld it. All you have are some cosmetic holes, you could simply put rivets in them, or screws. If you really want to fill them, Araldite, or similar, would be OK. Chemical Metal is also OK, but beware of using anything that would need sanding. Your mast is likely anodised alluminium, it should not be sanded.

 

[Tammany]

I've decided instead of going the polyester route I'll use epoxy instead with aluminium powder as a filler. Didn't realise you could get it until I was browsing my supplier of resins. You use it like you would silica or balloons.