Hi Bruce66,
I am now retired from development work but all my FSX and FS9 project source code is available from FSDeveloper in the Resources section for anyone who wishes to upgrade them.
Here is a link to download all FSX Native projects including the Mallard TP you show.
The source code is in Gmax.
https://www.fsdeveloper.com/forum/r...max-aircraft-source-code-for-30-aircraft.246/
Just a bit of silly fun! Love this plane - wish it was updated to today's visual standard but I very much doubt that will happen now - what with MSFS 2020 just around the corner and P3D v5 out already.....
I have a Grumman Mallard on the list of priority development projects specifically for FS2020. It probably won't be made for any of the P3D formats though.