On an ML7/5 I'd run a 120-130mm travel fork out of choice. Anything longer will make the front end feel quite slack unless you run a lot of sag. Besides, it was designed to be run with a fork of approximately 5" of travel anyway.
You could get away with a DUC32 by running it with quite a bit of extra oil in the air spring, so that the spring rate ramps up drastically, so that you would effectively be using as much as 50-55mm of travel as sag (so it would ride at the same height as most 130mm forks), whereas you would normally be running approx 35-40mm of sag. A 140mm Fox will have the same axle to crown height as the 150mm DUC32 though, so I'd steer clear of a 140mm fox personally, unless it could be spaced down to 125/130mm of travel internally like the Rockshox Revelations can.
Anyway, got a Durance myself… It's called "Medusa", and has a DUC32 fitted. The Durance was designed to be used with the DUC from the off, so the BB is slightly lower, and the head angle tweaked to make the bike feel more stable with the longer fork fitted. And it ROCKS! I had an ML7 before, and the Durance geometry is a good step in the right direction, as I felt a bit too much "on" the bike with the ML7, whereas with the Durance I feel much more "in" it, and it handles much better as a result.