In conclusion the A-138s could be one of the best tools for ‘real’ stereo panning and / or stereo balance adjustment, ‘to connect between a stereo source and the main mixing’. And as it seems that you have two (If I refer to your Percussion Row. I have only one but I don't blame you :)) we end up with a great additional... ‘Zero HP'.
Easter really is a beautiful day!
'On ne devrait jamais quitter Montauban' (Fernand Naudin).