While I don't have pictures to share, I will do best to describe what I use:
I have a piece of 2" x 4" screwed perpendicular to a wall stud. The top of this 2" x 4" is shaped to an inverted V shape so that it fits into the deepest portion of the grip and has a piece of leather glued on it to protect the grip. This way I am measuring draw per industry standards regardless of grip type. Also, the V-block has a thin wooden cap mounted on the end facing you to prevent the bow from accidently slipping off of it.
I shoot split finger, some shoot 3 under and others use a release so my string attachment from the electronic scale is shaped according to the individual shooting style. I use a hook for a release shooter, a solid (3 finger wide strap) of leather for 3 under, or a split (3 finger plus nock width) leather for myself. If I measure the same bow and only vary the string attachment, I will get 3 different poundage readings. It will usually vary by about 1.5 pounds. Does this make a big difference, not usually except to those that shoot on the edge of the arrows designated spine limits.