Dave,
Thanks for that, ..... a very informative. Lots of good sound advice.

Now I know what to aim for.

I'm going for 1 - 1.5 thou gap ....tending towards .001" (unclamped).
I won't really know for sure until I make it but I have a good starting point.
If .001" is slightly too large, I'll take a tiny amount off the adapters face.
So when it is clamped up the gap is negliable.
Well thats the plan. I think it will work out fine.

DaveH