Okay, I was thinking that the easiest thing would be to drill a hole into the strut tower and through the camber plate when it's aligned properly. Make it the same size as a cylinder of some sort - a big nail or small bolt or something. Drill one or two holes for each alignment setting, and then you can just stick the alignment tool (nail/bolt) into the hole to be sure you get it right. Do it at the alignment shop to get accurate street/auto-x specs. I'd do two holes for each setting, 180* apart, for the same reason I do more than one marker line.
My other idea was a bit more involved: put screws in the camber kit, and make stops that bolt to the tower. It has the advantage of being adjustable, but really you don't need that for the Contour unless you're messing with adjustable coilovers.
It's really not that hard. You can feel a relatively small amount of caster mis-match in the wheel, and I never have, so I must be pretty close with my marker.
