N+ 1 with D-23

I was wondering if anyone has experience with D-23 and N+ development. I am currently processing 4x5 T-MAX in D-23 for 14 minutes with constant agitation (Jobo). I don't seem to be able to get the highlights to move up to zones VII and VIII.

 

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Harold Todman

Are you using a sufficient volume of developer? Because developer activity decreases as the film is devloping, you may be reaching exhaustion before you get to a +1. If you are able, try adding 50% more developer to the drum. Or if you're unable to do that, use the devloper undiluted. See Steve Anchell's indespensible Darkroom Cookbook, page 114. If this doesn't work for you, toss the Jobo and devlop film in trays. It's easier than you think.