Shadow, you did a good job on that. As you figured out, having room to adjust the chain, to a tighter position is not an indicator of the chain being worn out. From the front, to back of our adjust system, there is probably close to 1.5in of movement that's possible, from the axle. The chain starts it's life, somewhere in that area, and finish is it's life in that span, too. There may be left oiver room, or not, but that part really is not important.
There is a spec that the chain needed to be, between pins, and it gets measured as such. Often times its the meaasurement between a specific number of pins.
I'm glad you figured out how to measure this. Pushing a chain beyond that point can often times up having the chain rip itself apart, and cause all kings of engine damage.