I haven noticed that as of late, Softimage no longer has their XSI importer for max 6 on their site. If someone could provide a direct link to it, or mail me at email@example.com I would appreciate it.
Already tried pysk's site, but it doesn't work with max 6, and I couldn't find it on maxpluginss.de, but i'll try again.
EDIT: found it, but it links to a 404, page not found error.
If you are making a new Mesh it would be easyer to just use the skeleton from Pysk's site and not worry about the importer but you will need the XSI exporter, I have Max 6, and Max 8 and every thing Importers and Exporters work great with Max 8 Thats what I use.
Merge your model into the .max file for the skeleton. This should keep the skeleton sized properly, and your model should stay in-tact as well. I find trying to merge the skeleton into your original max file causes problems with the skeleton.