So this didn't happen.
History, back around '95 or'96 I kicked my old Marshall quad down a large stairwell after a disappointing gig in Newtown, probably under the influence. Anyway the box held together but the speakers were even worse afterwards than they were before...go figure.
Not having stacks of cash, I could only afford to buy two speakers, at the time I chose the Vintage 50 (VS12), with plans to add two more later to make an 8ohm 200w box that would balance the 200w 8ohm EV in the mark II combo. That never happened either. I used the part-quad mismatched for a while and then it was retired to a friends place for about 15years. With two speakers set diagonally and the remaining spaces left open, it actually sounds ok.
Then the new plan. I wanted to finish the transformation to an 8ohm box to match and play through my mkV. A pair of MC90's became available, hence my original post. Unfortunately this was a pair of 16ohm jobs, which I didn't check until after meeting the seller. So I passed them up.
Disappointed, I then noticed a 212 slanted cab available on eBay, confirming the speakers were both Vintage 50watts, my original plan seemed to be back on the table... I could fit the box as 8ohm for use with the V.
Unfortunately, I would then have an empty 212 cab. Thinking options, I contacted the 2 x MC90 owner and picked those up.
So I've got some swapping around to do. But having played the ported slant box through my studio 22 I am having second thoughts about changing it out.
Oh well, can always change them back.
Please let me know if this post is too long and I will delete it! Not!