Getting a brake onto a Rockshox DHO!

Frustrating b_st_rd of a thing.

I'm trying to get a set of Shimano M755 4 pots onto a DHO.
Direct mounting the caliper with a 160mm rotor almost works but it needs to be spaced toward the hub, so I think apart from the spacing it's basically IS.
Tried a really old Boxxer 203mm mount with a 203mm rotor and the spacing side to side was better if a little out (but the Hugi hub is too close to the fork leg anyway), that's no issue I can't solve. Big issue is with the 203 Boxxer adaptor, the caliper is in juuuuuust the right spot for a 180mm rotor!

The radius difference looks to be 10mm with the 'boxxer' mount. Is this because of the 'Boxxer' mounting standard being different? Is it likely a 203mm adaptor for IS will put the caliper the right radius out?

Re:

DHO is a #3 Hope 185 front disk

Boxxer is a #6 Hope 205 front disk on a C2/E4

Not sure how this translates to modern standards...

Re:

http://www.oocities.org/ti_guy.geo/hope_calipers.html

Cheers! Didn't think of that. I'm going to conjecture that they're basically proto International Standard with the exception of the lateral spacing. There's an IS/IS 203 mount so I'll chase one down then I can use my pretty new RT-75DH rotor on it. I'm thinking I might have to have someone mill a bit off the face of my hub.