I've got one of those 80's half back cabinets. I love it. Mine has the MC-90 on top and an EVM-12L in the closed bottom. My recollection (and I hope I don't get flamed for this) is that the closed bottom was designed to be close to a Thiele dimension, so intended to sound and act like an EVM loaded Thiele. To me, that combination yields a great combination of clarity, warmth and presence. I had the matching 4x12, and there wasn't much difference in tone between the two.
That said, I am not a fan of the V30 in that cabinet at all. I don't think it generates the low end punch and depth/richness that can be achieved with that closed bottom half.
I did have a horizontal mondern 2x12 with V30's. If you play hard rock, and metal and plenty of chugga chugga, I suspect the V30 pounds through. But, I don't. I play a wide range of music, and the V30's are too mid forward and too narrow sounding to my ears as compared to the MC-90 and EVM, which are the other very common speakers that come "stock" or often seen in all these cabinets.
