I've had a Catalyst w/ dual AL framestays for more than a year, and had to play with the dual stays a little bit. I took an incremental approach. At first the shoulders didn't fit well, so I pushed the top back (if that makes sense). That was a little bit better. Used it a little bit more, and found that pushing in the middle of the 2 frame stays toward the front was pretty close.
In retrospect, it seems like if you could contour the framesheet / stays to you're back, you'd be pretty close.
Does that help? If not, let me know and I'll try it again or PM me.