The charts are typically set up for recurve and longbows that are not as centershot as the Diablo is. If you want to use a lighter spine arrow, move the rest out some more and let it paradox around the rest. The charts are set up to provide flecthing clearance around the riser. If you are setting it up closer to centershot, you can use a much stiffer arrow and get good flight.
Try adjusting the rest in and out with a particular arrow and you may find a spot where it shoots the best. Also, don't be afraid to adjust the nock point, you might want to start around 3/8" high, and try raising it from there, maybe up to 1/2" or more. One other thing, if your release is not clean, it will tend to make your arrow produce poor flight, espically with light weight bows. Try concentrating on a clean release, and see if that helps.