@Raz, just remember if you stray from the stock aspect ratio, you are going to change the rake/trail of the bike, which is going to make it handle WAY different. Even using the PP changes the setup of the bike due to the V shape of the center section of the tire, making the bike sit slightly higher.
I'm sure it's already been addressed, but don't try and run a 180 on the back of a stock 4.5 inch rim. It'll fit, but it pinches the bead, causing the tire to deform. Handling is crazy unpredictable. If you have the upgraded 5 inch PM wheels, those can take a 180.