For your average 4 seat flying club trainer a very good rule of thumb is to knock 5 knots off the POH gross weight speeds for an approach with a pilot and instructor and less than full fuel.
If we do the actual calculation for your warrior and its 63 kt gross weight POH landing speed and assume a landing weight of 1950 pounds which is the empty weight plus 2, 200 pound pilots and half tanks we get a new landing speed of 58 kts, or 5 kts less
.
You will find that the 5 kt rule will be very close for all the typical club aircraft. If the lack of precision offends you than I recommend you do the calculation for a minimum possible landing weight ( 1 person and 1/4 tanks), a mid range weight and the POH gross weight. A rough interpolation between these 3 numbers will be more than sufficiently accurate for your average club trainer.
One thing that intrigues me is the approach speeds you list for low flap settings. My Warrior POH only lists the landing speed at full flaps, which is incidentally the POH recommended landing setting. So I have to wonder if those other speeds are a result of the flying club "good idea club" throwing numbers out or whether there is in fact official guidance from Piper on the landing speeds to use at lesser flap settings ?