Archipelago is rocking and rolling now.
After some searching for support in the MT Support board I was able to figure out the correct settings.
Here’s the correct info for anyone else…
First, set the type to Metaweblog so you can send titles for your posts.
Site URL – the base URL. For me it was www.sitename.net even though my blog is located at /mt
Site Identifier – just the number
Path to Service – mt/mt-xmlrpc.cgi
Categories and hopefully some other goodies are coming. Thanks Daniel for this great free app!