I've put a scan of the Crosstop 3 manual here: http://www.retrobike.co.uk/gallery2/mai ... ewsIndex=1
(I'll also post it in the archive/scans forum).
I think the picture in the original post might be the Mk1 Crosstop, although it's captioned "Crosstop 3" on Bikepro. I have a Crosstop 2 (I think); similar to the illustration in the manual, but lacking the third pin through the 'dealie'.
Sheldon Brown's site has a good description of cantilevers - angles, mechanical advantage and so on - it didn't help me understand the Crosstop though.
Anyway, the manual says to use (canti) Love Levers, but does also give tips for how to set up the brake using Shimano V levers. I was unsure, so went for Real levers, but so far it works fine using the canti rather than V slot.