PAR_WIG1350,
I think the original picture is a slight optical illusion. I beleive the flange you are referring to is the C-channel that sits under the bottom T-slot. I have included another picture that should clear that up. The C-channel is within the same boundary as the T-slot.
All,
You do bring up a good point regarding the frame perimeter and the screw heads on our orange gusset plates. I believe we are ok on the sides and back, because the plexi mounts and screws push out the bumpers to same plane. However, the front gusset plates may need to be removed, because there is nothing on the top of frame to push out bumper to account for the orange gussets at the bottom front corners. Either that or we need to add something to top-front to push out bumper. Lucky for us, the orange gusset plates are extra structural reinforcement and decorative. So removing them, if necessary, is no problem.
http://picasaweb.google.com/MrKnauss...12952304481682