Thanks for the advice. I think the variables preclude a definite answer - without seeing the whole thing with your own eyes. Checked out the arrow tuning part on Masters of the Bare Bow 2 yesterday. Ken Beck reckons that if you've tried everything and you still get nock high when bare shaft tuning, it could be the string hand. When I've tuned the arrows till they fly dead straight etc, they still always fly nock high. From nocking point under centre to 1 inch above - nock high. Of course, fletches correct this, but that's not the point. He described EXACTLY what my arrows were doing - hitting the outside edge of the shelf. He described 2 things - both of which I have been doing. The first is pushing down on the arrow - causing a bend which tries to straighten on release - causing a vertical paradox. This, together with the usual, horizontal paradox, puts the arrow shaft right on the edge of the shelf as it passes.
The second issue is canting the bow, but not the string fingers equally - so the bow & string under the fingers are not parallel - adding to the problem.
My son watched my release and saw the problem. It's easy to see when explained properly.
Added to all this, an experienced trad friend of mine explained about the problems gloves can cause. The finger tip leather - especially on the ring finger - gets grooved, 'hanging onto' the string on release - same problem.
I love my glove, but may have to explore other options.
I have reset my bow to its settings before I started all the changes - which reduced accuracy somewhat. At least the arrows are now nearer the targets. Will work on the string hand.
Hope this helps a few others with similar issues.