I have been in discussions this morning with my Mastering Guru. Here is his reply to my question:
"Dithering is always a good idea when reducing ordlength, even if the difference will be @ -140dBSPL, imo. Can’t hurt.
That said, I’d NOT use UV22HR - noise shaped dithers are a bad idea when further processing is likely to happen - just flat TPDF dither is ideal."
He’s got a couple of Grammy’s to his credit so I trust his judgment.
So this leads me to my next question. Do we have access in Cubase to Dithering OTHER than UV22? Is there something else under the hood in Cubase 7.5?