Since you're considering HP5+ in D-23 1:1, you might find this discussion helpful: http://www.largeformatphotography.in...=1#post1368910 and subsequent posts.

I shared the development/contrast curves I discovered while doing a BTZS test with this combination. I'd be surprised if your results were considerably different. I shoot it at 200 since the difference between 200 and 250 is a mere fraction of an f/stop, beyond our ability to accurately meter a scene.