Nope, RHaseltine. Don't forget that Poser 4 can't read PNG thumbnails and that any mat pose that uses a jpg bumpmap will need to have the .jpg converted to a .bum first - a conversion you only can do in Poser 4. The main differencies between PPP and P5, when it comes to backwards compatibility is that the bump node is connected wrong when you use a PPP mat pose in P5. Apart from that, PPP stuff works great in P5 (though of course P5 has a lot on extra features) A few python scripts doesn't work equally good in PPP/P5, some of them work in PPP and not P5 and some the other way.

FREEBIES! | My Gallery | My Store | My FB | Tumblr |
You just can't put the words "Poserites" and "happy" in the same sentence - didn't you know that? LaurieA
  Using Poser since 2002. Currently at Version 11.1 - Win 10.