[alistairsam]

Hi Rolf,

Thanks, you're right I could use a square central and circular upper brace and achieve the same cone.
But have a look at the attached which roughly shows the direction in which I see forces being transferred to the dovetail bar along the square and along the octagon.
if this is considered, then either a circular or octagonal central would appear to transfer the forces better than a square as corners aren't involved.
My engineering background is electronics and not structural so I could be wrong.

In your case, the dovetail bar is quite wide and may not be such an issue, but with my thin bar and the heavy guide scope it could be an issue.

I might be over thinking this, but its better to consider these factors at this stage rather than later.
My objective is to build as light and rigid as possible as it will be transported very frequently and not fixed permanently.

I'll also be using this on a fork mount as well as on a heq5pro.
the fork mount can easily take heavy ota's, but it'd be on the limits of the heq5pro, hence the obsession to reduce weight.