Here's a thread where the transition is discussed:
http://www.3fatchicks.com/forum/sbd-...-p2-combo.html
I think there are other threads which discuss this. Try a search in this forum. In my view 1.5 is not anything official but an inbetween where you are adding items slowly to figure out what works with your body. For example I found I can't eat oatmeal in the am...it sets off cravings and feeling hungry all day but I've found I can enjoy oatmeal for dinner...something we often do on Sunday night. Many times beachers here will go back to 1.5 after holidays or events where they overindulged...as a way to kick back in without going back to P1. I do fine with all fruits and don't feel a need to cut them out at any time but often will cut down on my grains.