No time yet, but I've purchased two MLV in the two thicknesses, and I'm sitting on piles of MDF and scraps, and have my own install actively going on, so there's no physical barrier to building a rig for sure. Just time constraints.
I haven't built anything yet, but here's my test rig I've worked up in my head:
Two boxes. Really three if you count the one a test speaker will be in.
Box 1: will have my calibrated mic held inside. Shouldn't really need to be totally enclosed but we'll see. Will have a 6" hole or so in the other end.
Box 2: basically will have a 6" hole in each end. One end will be used to sandwich a piece of MLV between box 1 and 2, boxes screwed together to hold it tight but make it easy to swap MLV.
Box 3: a test speaker (probably a 3") firing into the 6" hole, screwed tight to box 2. I have a bunch of knocked-up test boxes that I don't care about screwing through.
That way, all the sound will be contained in box 2 - other than sound leaking through the MLV.
I'll do sweeps with REW.