Thanks!
I risked the putty marking up a high end guitar I have, Martin Authentic, but put the piezo on the pickguard so any residue from the putty might rub off. It sounded pretty good but not worth the mucking around - I just couldn't get any level.
But I think the best file I currently have is from my 59 LG3 with Martin Thinline undersaddle. I keep returning to that one!
Weekend approaching - who knows what we could get up to.....
BluesKing777.