Jay Dyer used to be a Dimondite, and was even going to join their "monastery" at one point. He was a sedevacantist for years. He knows their position and it's arguments far better than the Dimonds know Orthodoxy. He won't debate them, but I forget why. I want to say that they never responded to his request to debate years ago, but I could be wrong. I also believe they refuse to debate him in return, probably saying he is "of bad will," which appears to be their evaluation of anyone more educated than themselves.
Ubi Petrus, however, who has several refutation videos of Dimondite claims, has publicly challenged them to a debate recently. I would certainly watch it, but even just watching the Dimond videos vs th Ubi videos, it shows that Fred and Bob are seriously outclassed. A debate against Bishop Sanborn would be far more interesting.