I created a style which was fairly minimalist (no userpics, very little markup, no tables, etc.) and it seemed to work out all right. I also had &checkcookies=true at the end of the URL (and it worked in the preview in my real web browser). I also tried to login from my PDA and got a result page (after the next sync) saying "Hello, pne". But still I didn't get friends-only entries when I viewed the page on my PDA.
Also, the links didn't seem to work properly -- I changed the links to include &usestyle=lynx for a "lighter" format, and that worked, too, on my browser, but not in the PDA. So it tried to display the left-hand navbar and indented entries and userpics and all sorts of stuff I didn't want.
After a couple of tries I just gave up and removed my custom channel again. Pity; it would have been nifty.