I've been using FSNav 4.7 for years now, and I HIGHLY recommend it. For those with systems that are pushing their limits, I recommend it even more, as it uses far fewer resources that Plan G does. (...not knocking Plan G here. It just uses more Horsepower)
FSnav is a good idea too if for some reason you find yourself flying online and the Control does not want to hear reasons and demands of your DC3 a complete modern day digital navigation compliance ... or at least emulation (and it's happened).
And it's better to have FSnav available in such a case, than trying to use other tools like VASfmc.
One half of me can't stand the other... and is in search of allies.