I can't really add much except that around 26-28 years ago I fished an Angus loch a few times for Char and we used lead core lines and a team of three flies. The fish normally held 30-50 feet down and were taking the flies as they started to rise on the retrieve. Almost like feathering for Mackerel.
Flies were Alexandria's, Teal Blue and Silvers, something with a red and white wing (Something Belle maybe) which I cannot remember and I have never seen since and silver Wickham's Fancies.
HOWEVER, I also used to do a fair bit of walking around the same loch and for brief periods of time the Char would be up near the surface feeding on flies. I seem to recall this being late summer time, but could be wrong. There were people fishing at that time and catching them on dry fly and nymphs.
So, basically, fish deep or shallow, with wets nymphs and drys..lol...not much help, sorry.