Thanks Peter...
There are lots of good bits of kit out there which would aid flight safety which the FAA have STC'd for that particular aeroplane. It seems nuts that one cannot then buy this piece of equipment and just have it fitted.
Probably the ones to ask are the avionics installers but I'd like to get it clear in my mind before because there is an awful lot of teeth sucking and "can't do that"'s that I hear!
For example EDM800 looks pretty good, and there is an STC that covers it for the aircraft. So how exactly to I know if I can fit it or not? where do I start? It is all a bit of a minefield!
Cheers