just save your runtime folder and then dump it into the new p5 directory; I expect that'll work. For what it's worth, I've moved my whole p4 folder around on my hard drive without a problem, and renamed it as well (it's called "poserpro" so I can have a non-propack p4 installation separately for testing stuff in). Python scripts should reside in the python dir under runtime so they should be ok too. Keeping both installed only seems like a good idea if you want to do something in p4 that's no longer supported in p5. (nothing comes to mind, but you never know...)