Bob
I'm a bit mystified as I have some of our school club 66's on plastic elements and thats with the standard foresight, I can't go and check them as they are on school holidays at the moment, I can remember drilling out elements to get the correct size but as far as I can remember I di that on standard plastic elements. I have loads of foresight ring retainers from various rifles, although probably not Originals.
And it makes no difference which way round the element is fitted as long as it fits and is centralised.
PS. A classics man like you should be using metal elements any way!
regards
Robin