Without adding significant amounts of noise to other WFS loops I have engaged the MC2_TRANS_PIT and YAW loops. 

After several attempts to measure the system response and computing the output matrix, none of which gave any useful results, I gave up on that and decided to find three orthogonal actuation vectors which enable us to close the loops.  So using the last good output matrix (below left side)  as a template, I rounded it off to the nearest set of orthogonal vectors and arrived at the following matrix (right side):

I also decided that WFS1 and 2 need not drive MC2.  This is just to decouple the loops and minimise cross-talk.   This (albeit heuristic)  matrix seems to work pretty well and the real matrix is probably quite close to it.

I show below the suppressed error signals after tweaking the gains a bit.   The blue line is with no WFS, the green one with only WFS1 and 2 loops on, while the red is with all loops turned on.  The WFS1Yaw and MC2_Trans_pit loops might benefit from a more careful study to determine a better output matrix.