I may be wrong here, but I always measured the length of pull from the middle of the trigger (in the curved part) to the Center section of the butt
plate. Thus a flatter type buttplate rifle such as a Lancaster & a Hawken
buttplate will measure the same this way if they are say ? 14" L.O.P. when you measure it this way. However if you go from leading edge of trigger to end of the butt at top or at bottom, on a Lancaster & then do same on a Hawken or Tenn. rifle, the latter will have a much longer length of pull. So it should be center to center. As tall as you are & with long arms as you have, you will probably end up with a 15 1/2 " L.O.P. and 3 to 3 1/2" drop to make it comfortable. I wear a 34" sleeve & I can shoot a 15 1/2" L.O.P. in certain rifle styles, then a 14 1/4" fits me best in a Lancaster, etc. But I like 3allot of drop in all of them. Best to go & try out several. :-)