This is totally one of those tricks I didn't know if I was ever going to get, but fortunately Leo's recent video on body tracers showed a possible shortcut that worked out beautifully: by treating each side of a behind the back waistwrap as a 2-beat, one can train each hand to do its part of a behind the back crosser. The result needs some cleaning up, but it's a useful shortcut for folks with inflexible shoulders like my own.