Hello Ray,
some good, some bad.
Looks like the free version of VS2015 requires registration and login to the Microsoft "cloud". I don't like that so, at least presently, I abandoned it and reverted back to VS2010.
Tried to compile it and got back tons of warnings and errors, as expected.
I briefly went through them all and, especially warning messages, are a lot, but grouped together into 8~9 big "families, so actually 8~9 warning messages have to be considered and eventually fixed.
Errors are quite few. Some are due to incompatibilities P3DV4 introduces, some are not but I haven't analyzed them yet so I don't know how hard will be to fix them. Consider I must maintain backward compatibility, at source code level, with the 32bit version, so changes have to be carefully studied and implemented.
At the end I must say I have a positive feeling at the moment so, time permitting, I'll keep fighting

. I'll keep posting in this thread any relevant news.
I'm currently looking for a good freeware jetliner supporting P3DV4 to be used for testing. No payware and non too complex. Any suggestion?