Hello Hugh, Be sur that your 3mx and 3mxb files are allowed to be served by your IIS. If not, you get a 404 when you request the URL of each of them . To allow permission to serve these type of files by your IIS you have to add the correct TYPE MIME…

Fence clip works best but it doesn't have depth so it shoots trough everything and you have to rotate view so there is nothing in background which don't need to be clipped. 3D Fence clip would be nice option.