I have a 26 inch Hunter built with 42mm bearing holders spaced at 100mm. If I were to build a wheel around the Nimbus Disc Hub do you think the deflection of the holders out the additional 25mm would create too great an angle in the holders to work properly?
You could cold set (bend) the frame and it would probably work. 25mm is a lot for a 26" unicycle, but the worst that could happen is that the bearing clamps wouldn’t be quite straight, which might affect your bearing lifetime. A decent frame builder could get it aligned properly for you, but even doing it yourself with a 2x4 would probably be fine.
The Oregon frame is relatively inexpensive, the Hunter frame is not. I’d either get the Hunter rebuilt or sell it to buy an Oregon.
Seriously, you need more than just frame width at the bearings, you need frame width for the disc, you need a disc brake mount…
You could also add the MountainUni disc brake kit using the bearing holder disc brake mount, that would be the easiest.
Or you could buy an Oregon 
Or you could wait a little and get an improved Oregon that will not break after little over two months. 
sour puss 
Hey thanks, free lemons.
Ah, that’s much better now.
I think it’s actually one word: sourpuss, not sour puss.
Or Weld a mount tab onto your 26" Hunter
Or you could keep your 100mm hub, weld on a steel tab mount to your Hunter, and continue with Nurse Ben’s suggestion for a Mountainuni Disc. See attached pictures. Thanks Ben 
auto correct what wo gonna do
also whlist were on the subject how on earth did you break it !! im acctully kind of impressed
I already own an Oregon - Rick Hunter frames are not that expensive - I never seem to do things the easy way and I like the clean look of the disc inside the frame - May jsut have Hunter fab up another frame with the spacing at 125 with brake tabs.
Why not get a couple more wheels built for the Oregon, mount each with a diffent tire, then you could swap wheels for conditions.
I don’t ride the Oregon hardly as much lately after rediscovering the 29er love ; and of course I have a 26 guni too.
How about putting a guni wheel on your Hunter?
Something to consider. Although, my climbing skills are already suspect even on light grades and I tend to ride trails with almost no flat so I don’t think I would get much use out of the high gear.
How is the Guni working for you, now that you have had a little time with it?