I rated Delta 400 @ 400. That's what my Diafine box recommends. Not sure why I rated the 100 at 50 since the box says 80. I might have changed my mind about how I was planning on developing it.
'From my experience, you lose a lot in terms of tonality and shadow detail for the benefits of higher speeds, and if you don't even get higher speeds with the Delta films, it seems to not make sense. It would seem a waste of good film to use it for Delta.'
With TriX and HP5, you get the speed boost, but you lose should some shadow detail. With Delta, you get no speed boost, but shadow detail does not seem to suffer. The negs are fairly dense. The results of my limited trial were inconclusive at the time, but I think now I know enough about scanning that I could get good tonality out of Delta 400 in Diafine.
It may not be my first choice for developers but in terms of shelf life, flexibility and economy, Diafine scores high.