I have not noticed any differences in the FPS between v1.2 and v1.3, not that I really looked. I do get better frame rates with the VC-137 and E-3. I assume that it is because they don't have the passenger cabin or cargo deck, only the VC. I also get better frame rates with the -300C, I assume, because the cargo deck has a lot less polygons than the passenger cabin.

Maybe you need to try the http://www.venetubo.com/fsx.html tweaks to see if you can improve the performance.

Mark