Great stuff. Working for me in WinUAE. Will test in real A1200 later.
Just a note: If you use Retroplay's WHDLoad pack updates. The are some cases where the zip of the game, e.g 'ClueAGA', unpacks to a folder called 'TheClueAGA'. If this is in your 'C' directory, as it was mine, this results in fastnav displaying ABCTDE... Easily resolvable at the user end, just letting you know.