Java, I got my new stand up and running...
So I set up the BMBH and I can see (feel) the difference between having the top rings set at 9' and say 8'8". My measurements are skewed a bit because I made my legs longer then the stock legs. Im working with 24" legs which brings the fixed eye of the sling with the rope thimble out another 3" on either end.
SO... to simplify.. at a distance of 9'6" between the fixed eyes (which is where the top ring would normally be) It felt really good. Im broad shouldered so its a bit of a squeeze, but not to bad. I then dropped it down to 9'3" between the fixed eyes and it was very uncomfortable. Amazing what a few inches does for comfort.
I can see having a RL between the fixed eyes being just as advantageous to set up the BMBH as it is on a gathered end.