I shot Delta 400 in 4x5 for the first time recently, and I exposed it at E.I. 200 as I used to with T-Max. It turned out to be significantly overexposed when developed 12 or so minutes in HC-110 dil. H. Your tests may vary, but you may find that 12 minutes is a tad too long. Maybe try 9 or 10 min. to start?
Then again, every time I have gone to someone else for developing advice I get more answers that I know what to do with. Good luck. I'm going to continue my tests so that when I make the inevitable switch to Ilford films I'll know what I'm doing.
EDIT: I should say that these 4x5 sheets were tank developed with five gentle inversions every thirty seconds after a first full minute of agitation at 68 degrees F.
Was that Ilford Delta 400 ? I thought it only excisted in 35 mm and 120 size. Delta 100 , FP4+ and HP5+ are available as sheet film as far as I know.