This is possible, I can’t help with your setting, but I operate a similar scenario with my Lotus Domino mail. I use Commontime and a Verizon Treo 700w. I have 2 connection setting. 1 Cradle/USB – All mail is sync’ed that is less than 2 weeks old, attachments and all. A second connection, Verizon Wireless: Sync only message headers and text.
Check the software settings and try to create a second setting for messages only.
Hope that somehow helps.