I was wondering if anyone has ever seen a VX-351 mounted parallel to an MMV, or has any bright ideas on how to get it done? The aim is to basically expand the MMV panel to the left, in a similar fashion to how it was 'done' on the XL. I guess alternatives could work, like, attaching it to the top.

Perhaps there's a mounting device (like an arm) that can be connected to the back of the Voyager, or the keyboard stand it rests on, and act as a 'top tier', but not the usual 2nd keyboard tier, as the VX needs to be locked tight, so patch cords can easily be fiddled with, without having to hold the VX.
Please note that the Voyager is studio-stationary, and does not travel. So irregular size modifications are not a problem.
Meh...