On 10/05/2021 14:57, me wrote:
On Monday, May 10, 2021 at 1:48:19 PM UTC+1, newshound wrote:
https://www.alvinkeyclamp.co.uk/prod...ing-base-a12-6

That's exactly the sort of thing I was thinking of but the rail is oval and the rail needs to be attached horizontally

Then chose one where the pipe is about half the minimum diameter of your
rail, get say a six inch length of pipe and bore into your rail to suit,
securing it with a couple of vertical cross-bolts. Dome headed on top,
counterbored underneath to conceal the nuts. You might want large
diameter washers underneath to reduce the risk of rail splitting.