Having added a few more 1/64th ply biscuits the framework was a lot stiffer, however I still wasn’t happy about the strength at the “break” line so I removed the cross braces and epoxied some carbon fibre tows over the joint.
Now that’s a lot stronger!
This raises the question why didn’t I do this in the first place? I go on at length about the virtues of carbon fibre tows and then I fail to spot this obvious application; must be something to do with age!