I managed to get the 90 day trial version of Visual Studio 2008 and figured out how to build x64 versions of the plugin. http://www.farfarer.com/blog/2012/06/12/unity3d-tangent-basis-plugin-xnormal/
Sorry this took so long, the Visual Studio project ended up with wrong settings somehow having set it up in 2008 rather than Enterprise but I finally sorted it out (it's all complete jargon to me). Also discovered the versions I'd released previously were still in unoptimised debug mode, so hopefully this'll be a little…
Well, you won't be able to fix this with Maxscript or on the Max side easily. Importing .FBX files, you have to export them with normals, tangents and binormals otherwise Unity'll generate it's own. You can fairly write an Editor script to set models to always import tangents on import, too. Also, Unity doesn't import the…
With the help of the Unity devs, I've managed to get this working right. Got some final tweaks to make to it to speed it up some more before I release it, though :)