First of all, thank you PMDG for delivering such a wonderful product! This is definitely the best ever addon developed for FSX, as advertised! :) However, there seems to be a problem when I am trying to add the Feelthere MAP! to the plane. There is a configurator in which I can select which planes I want to install the MAP function too. It worked fine with the PMDG 744. For the NGX, it only shows the -800NGX non winglets, the other variants are not shown at all. Even after selecting the -800NGX to install, it comes out as nothing again. Has this got to do with the aircraft.cfg being "read only"? I've checked all 4 aircraft.cfg and the "read only" box is not checked.

So glad you are enjoying the airplane. If the read only box is not checked, then the aircraft.cfgs are not read only. You may want to refer this question to the FeelThere forum.