I've decided to package all my plugins as .xsiaddons. This should now allow them to be installed in a workgroup and easier to uninstall.
2d Dxf importer for XSI v6 - here
3d Dxf importer for XSI v5/6 - here
Sun Position plugin - here
(Now features Primitive > Light > Sun and Property > SunPosition menu items. The Sun primitive features a "distance" parameter for moving the light clear of the scene.)
Four point rotate - here (Post coming soon about how to use this plugin - it's a CAD style precise rotation tool.)