Try a Loch Ordie, Bibio as previously suggested, big dry daddy or a sedge pattern. Don't discount the use of wet's.
Maybe Zoomer can put you onto a wee loch with a good head of wild trout. I would maybe suggest Swanswater or Carron Valley reservoir however but if you want to head up a bit from Callander, Loch Earn has been known to be quite productive with the fly.
