Fletch, you have a very good point! Your last sentence is good enough for me, Both ways work!

I just went out and drew two of my longbows, one at 51 the other at 55# at 27".

I shoot one index over the nock and two under.  

What I saw when I did this was that the bend point was around my middle finger.  It makes sense since I put very little pressure on the other two fingers and there was virtually no curve around the group of three, just a bend at my middle finger.

I don't think there is any real difference from how I draw and using the s hook to measure.

You can actually use a bathroom floor scale. Use a 2x4 with a notch cut in one end and marked at 28". Put the bow string in the notch, set the 2x4 and the bow on the scale and reset it to 0 . push down on the riser to the 28" mark, should give you an accurate reading...PR

Quick, easy, and above all economical!