Hi hancop, i had some SIG CA hinges in my LT-40 kit i built a few months back. I ended up ditching them and installed some du-bro pinned hinges instead for which the kind of tool campbec mentions is for (Dubro hinge slotter). This tool has a nifty guide which will center and correctly align the slots. The results were good in terms of how the surfaces lined up but i ended up leaving quite a large gap between static and moving surfaces which i later needed to seal (my own inexperience and not a problem with the tools). However I don't think the Dubro tool would work well with CA hinges as the thickness of the slot it cuts would be too wide for a wafer thin CA hinge. Maybe theres another similar tool for CA hinges?? I'm going to experiment with hinge points on my current build (SIG Kavalier) there's some really good information on this site:

http://airfieldmodels.com/index.htm

Although no experience with them I get the feeling that CA hinges are quite forgiving if not perfectly aligned because of their flexibility?