At the TRAPHX launch, I also picked up a KBA M3500R reload. This is one of those motors that I found a thrustcurve for, fell in love with, and then was disappointed to discover was out of production.
I wonder if it would be possible for Aerotech to make a similar motor for the 75/7680 hardware. What's really surprising to me is that the M3500 has more than twice the thrust of the only slightly smaller M1550. As far as I know, all manufacturers use the same case thickness in 75mm, so I doubt the M3500 is running at a significantly higher pressure, but that's really the only reason for it's high average thrust that I can think of, unless Aerotech has a faster burning version of Redline that they're sitting on.