Colin,
I had asumed that there were about 40 bolts 'sewing' the ring to the hull as with bigger tanks. That would have been plenty to hold the layers together. In WW2 it was usual for the bolts to be fitted from the top and have slotted, countersunk heads so that they didn't stick up above the ring, nuts on the bottom. Then they started screwing them in from below into tapped holes in the ring. I hope the turret is just free to traverse with just a brake /lock to stop it. If it had geared traverse that is a whole minefield in itself. I will be fascinated to see the detail of how you make the ring as it is quite a challenge to get it spot on.
It might help that in Valentine production they used a device that was suported on a bearing fixed to the tank floor and another above the hull roof but fixed to it. The device was free to rotate on a vertical axis between these bearings which could be adjusted so that the axis was exactly in the centre of the turret ring. There was an electric grinder mounted onto the rotating part that was used to true up the hole that the ring would bolt into. Vickers did have a vertical lathe that would turn a whole tank hull but possibly it was needed for other jobs. This concept might be usefull here ?
David
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