Warrior POH only gives details for MTOW (2325 lbs).
As you get onto the bigger Pipers (Seneca, Aztec) the POH gives a constant speed, with weight affecting Landing Distance as opposed to approach speed.
So - as Ghengis says, go with the book speed, maybe a little less if you're light but definitely not below 60. You'll find that weight affects landing distance more than it affects approach speed.