So after finally getting the 5x5 mixing box, I thought I'd try to print some MF and 135 negatives to see what a difference it made. The answer is: very little; less than 1 stop. In conversations with the folks at KHP Photografix, they had said that when you have a multiple bulb enlarger the smaller mixing box does not make nearly as much a difference as it does with a single bulb unit. Pretty much what I found out. Still, I'm glad to have it. In Emails with the DeVere folks in the UK, they said that they made very few of the 240 mixing boxes because there just wasn't a demand for it. John said that they didn't make very many of them, and no longer make them.
No, but still happy to have the option. Last nite I was printing some MF negatives with the 80 Apo Rodagon. Was getting some pretty long times, forgot I had it or I would have switched to it!