Nice conversion, Peter. A neighbour of mine has one of these monster dishes overlooking my yard, and I too have eyed of the same pier mount!
Arc or Mig weld? Not that it matters, just like to know what others use.
Would you consider anodizing the aluminium or powder coating. Sure not diy jobs, but tougher, more polished finish. Anodizing can be a range of 'electric' colours: blue, yellow, hot pink, red (good for dark adaptation,
).
Mental