A pound of rice hulls would be silly. Likely you'll be ok with zero, but if you need to feel like you have the same amount of filter material as an all-barley mash, you'd want to add hulls at a rate about 6% of the wheat's weight, about 4oz. I've mashed 60%+ wheat grists with no added hulls and had no problems lautering.
Wheat tends to settle at a higher pH than barley base malts. Some acid or acid malt would take care of that.