There was such a mod someone was talking about.
I don't recall the details, so apparently it didn't leave me convinced.
... or maybe there was supposed to be follow up, and I missed it.
edit: in Robby's post above, he linked to the thread in question.
Just why the CK1's, 741's, and 621's of the world don't do as well on Ku, at least on prime focus dishes was due to their narrow view of the dish,
I thought.
So, the C-band feed saw the entire dish with an F/D of .3 or .4, but the Ku portion acted like it had an F/D of .6 - .7, and only saw the center.
Properly installed and centered, they -can- do quite well, though.
So anyway, you'd think the Ku would see an offset dish just fine.
Never seemed to work that way.
Another factor that was brought up, had to do with the Ku feed decreasing the C-band signal just a little, compared to a C-only LNBF.
Not sure which of these points are true and which are conjecture, so you're on your own.
