Hi Bazz, I don't know much about the Durst enlarger, but had problems with my De Vere 4x5 when I first saved it from the tip. The mirror, which is placed at 45 degrees in the path prior to the diffuser was old and gave me blotchy uneveness due to a loss of reflective film on the mirror, and I bought some very hard to find globes. May I ask what you are rating your Hrt green film at? I use the same film and have settled on ISO 80. I gave up on tray developing for 4x5, could not stop the blotchy results and turned to rotary, which works well at 1:150.
Here are a couple I took yesterday at a local car meet
One is out of frame slightly as I was sitting in the middle of the road apprehensive of getting run over by a hot rod.
I used a Sironar N 135mm and a Kodak Commercial Ektar 8.5 inch, the ektar surprised me and will be used a lot more frequently now.
Cheers Andrew