v2.5 of Mixbus is out and it adds the support for loading multichannel vst plugins inside it.You can use it without having to edit the .xml file. By the way I'm having some troubles.When I load nebula on a mono track everything is good but when load it on a stereo one I got an Runtime error and mixbus crash.I think the problems is related to nebula because all other multichannel plugins loads fine.The plugin itself loads fine but when double click on it to open the gui I got the runtime error.I try to update to the last Visual C++ but no luck.I'm on Windows 7 and I'm using the latest nebula version(.712)
You turn the 64 Nebula vst via jbridge (http://jstuff.wordpress.com/) into 32 bit Version, because, as you said, H******* is 32 bit and accepts only 32 bit versions. These "downgraded" versions work. before that you should move the original 32bit nebulaversions out of the vstfolder you pointed Mixbus to. This is meant as a workaround, not as a solution.
Atm i try to chain reaper and Mixbus via Jack, which would also be a workaround, but if its good maybe i keep it that way.