Bob Dodd WAS working vertical clamping for aluminum by taking the first extrusion off with his older Desktop(with single Y screw running down the middle like mine) see #32 ;
http://www.talkshopbot.com/forum/sho...9881-Dovetails

I know the new Desktops and Max's have dual ball screw on the sides for vertical clamping. And Bill Young is actually working with a factory made jig.
scott