Okay, what I think I will do is not have an upgraded KDE on the disc
Strongly agree. There are several kde apps on the repo that make you upgrade to 3.5.9. That is a bit of a pain, because it also upgrades qt, which in turn depends on mysql, which is still in testing (correct me if I'm wrong).
This means a simple kde application (even just installing arts) on a 5.9 Std fresh install makes the user enable the testing repo, upgrade core libraries, and install a database. I think that's a bit too much, and that all kde applications should be compiled agains 3.5.8.
EDIT: Sorry, dweeberkitty, didn't read that "[you] didn't really build any packages against the newer kde packages". That's great.