I have the right angle Neutrik plug in my Mad Dogs, and the opening on the cup didn't need to be enlarged anywhere close to the 1.5mm difference you mentioned. It took just a small amount of enlarging with a #11 X-acto knife, and I would estimate that I opened up the hole just 0.3 mm.
A few pages back in this thread I posted a close-up photo of this plug inserted into the Mad Dog ear cup.
I did read your post. I just don't feel like making irreversible modifications to my MD.