You can give this a try:
Delete your raid0. Recreate Raid0 strip But ONLY select 200 - 300 gigs (believe they refer to this as short stroking) for operating system and programs. Keeps the Progams and operating system on outer 15% of platter. Select a strip smaller strip size say 64 K. This increases the probability that a file will be placed in to two strips - If the file fits into one strip Raid0 provides no benifit. Then select the remainder of the drive for a 2n Raid0 strip. This is somewhat similar to partitioning a drive.
Also you might try increasing cluster size. I think default is 4 K. Maybe try 8K cluster. This increases waste on very small files, any file less than 8 K will still take 8K disk space, but the advantage is that on all files greater than 4 K the number of clusters read is reduced by 1/2.
Note on my setup access time is reduced to 9.x mSec verse 11 -12 mSec.
Added: I'm NO expert on this, I've been using Raid0 for about 8 -> 6 yrs, but always just taken defaults - Maybe a expert can verify, or tell me I'm all wet.