Ok so, as mentioned above, I decided not to use one of the already developed overlay apps (OVRDROP, DailyVR ETC) to bring in my GliderNav into FS2 because:
A) They cost more
B) They are not really designed for this so very clunky with bigger overheads on performance
C) I can have full control over how I want it look & work.
So I scrapped my original windows based GliderNav app and spent a bit of time today (not as much as i wanted) working on my own VR overlay system and only just had time to capture something before I had to go out.
But this shows at least it working, this is my own overlay showing a full moving map (streamed in real-time). The video shows some jitter/movement between the map and the cockpit but this DOES NOT happen in the sim, so must be something of the SteamVR window I used to record it.
So now to get to work on the map itself and the size/positioning within the cockpit.
And sorry for the "shaking", thats me putting my headset on and then off.