I've been thinking too about using aluminum to make the frame. Wood, because it is prone to warping and humidity changes, where as metal is not (at least not enough in this case ).

basically, I'd be looking to make a contact frame like this one

http://cgi.ebay.com/10-1-2-x-8-1-2-C...3286.m20.l1116

just in aluminum, and probably powdercoated or anodized to minimize reflections.

what do you guys think?