The pier is bespoke – the farmer/astronomer who made it and welded it all only made 2. Not a commercial effort, but I managed to buy one from him when he gave up the hobby for a while.
I think the only bit easily modified will be the metal plate supported 3-4″ above the top on 3 thick bolts. I looked at upgrading the bolts once and found they were a weird Imperial threading, so will reluctantly stick with them and – if need be – create a new plate from scratch.
Anyway, the rest will wait until winter now then. Will post more then…