What we are seeing right now, but not yet definitive, is if you run 2.5 before the HOT Fixes, or only have the first Hot Fix installed, you will have issues. If you just did a fresh install of the latest 2.5 with all the fixes included, it seems to run fine. So, if you wish to run it in 2.5 to try it, it may work, or it may not depending on your updates or freshness of install.
My point above is we have no way to support any issue that you may have in P3D since none of the team has it, and internal interfaces as still evolving and being released.
So far, testers having 1.4, 2.3 and fresh/very recent 2.5 installs seem to run okay.
There is no difference in the FSX package for P3D so give it a try. If it works, great. :-)