I am thinking about using the Fralin Blender pot on my Strat, but I have the middle pickup RWRP. I have heard that using a blender pot will negate the hum-canceling effect of the RWRP? Is this true or a hoax?
Nope. It will have no affect on the RW/RP middle pickup but if you are blending the neck and bridge pickups, you won't have RW/RP with the stock pickups because they aren't RW/RP to each other.
There are a couple ways around that: you could switch the bridge and middle pickups or the middle and neck pickups, depending on if the #2 or #4 being RW/RP is more important, but there's no way you could have three pickups in a strat where the neck+middle, middle+bridge and neck+bridge are ALL RW/RP without getting really creative.