The first thing you should do is make sure your bow is exactly set to specs. On your XT, I think the most important factors are ATA and the cam timing. Let the brace height fall where it may. I could be wrong, but I don't think so. If you don't know the specs on your XT, go to the Mathews forum and find out. Also,check the idler lean. Make sure the string is coming off straight at full draw.

The second thing you should do is lose the WB, just kidding, no really lose it.
Using a fall away rest will give you the several fps the WB is robbing you of, not to mention the other issues related to the WB. I won't go there.
For all you Biscuit users, its a great rest.
Good luck man!