Many thanks – you forced me to go back and check. I thought I had change that disable a few days ago, but obviously I messed up somwhere.
All working now … so thank you.
Controlling teh AP w ith a Stream Deck, allows one to see exactly what the AP is doing and control it.
Heading 360 +/- 1 deg
Altitude 2000ft +/- 5ft
IAS is out of range for the Spitfire currently 279 (which is overspeed for the C172 - C172 Stream Desk Page ).
Now if only I could get the Transponder to be active, I could fly the Spitfire on VATSIM !!
What are the chances that Vatsim would allow a Spitfire without a Transponder ?? 
Radio freqs can be set with the Stream Desk, and I assume the spitfire could also fly a FP, if one was loaded, although I do not see at the moment how one could select the leg – would just have to fly the whole plan… and refer to the VFR Map
I am thinking a Spitfire, flying around on OpenFs, flying a FP on AP, (so rock stable legs), that other spitfire could practice formation flying with.
Adding SP speed control would really be the Icing on the cake, but is probably not 100% necessary, as the speed will remain stable, but at some undefined amount.
FUN Stuff.
You could even record a AP flight on OpenFS, and then play it back, and practice formation flying with your recorded plane.