Whittler, yes you can, but a 10" taper from 11/32 to 5/16 will only lighten the arrow about 10 to 15 grains along with a couple pounds spine. Unfortunately, it would remove the weight from the front of the arrow, which doesn't help with good arrow flight.
I have two thoughts on why tapering a shaft helps with flight. First, it removes weight from the rear of the shaft which helps FOC and seems to quicken arrow "recovery". I also think tapering has the effect of "tillering" the shaft, making it flex more evenly during the shot. It's all theory, but that's my take. I tail taper all my shafts.