Questions about RAID and Cache Disk.

I´m going to be editing P2 HiDef footage. I have 5 hard drives installed in my Mac Pro. I have the XRAID card. Four of my disks are connected to the Raid card, and my fifth disk is connected to the SATA cable underneath my Optical Drive.

Currently I´m running like this:
Bay 1 - 4 are connected to the RAID card, but only 2 - 4 are running RAID 0

Bay 1: System OSX disk
Bay 2 - 4: RAID 0
Bay 5: Cache Disk for Photoshop and Premiere, and After Effects

Would I be better of to put my OSX on the Bay 5 (benath optical drive), and but all (1 to 4) raid disks in RAID 0 configuriation, and run both videofootage AND cache from this RAID 0? My question is: Would my comp run better with cache and videofootage on a fast 4 disk RAID 0, or is it better to run the cache seperatly from the NON-RAID disk?

question 2:
Is there any difference in speed running OSX from a non-raided disk connected to the XRAID or just to run it like a regular disk connected to the SATA cable beneath my optical disk? Does the XRAID in any way boost perfomance on a non-raided disk?