Avoiding sag in plywood desk

[kliu]

I'm working on an L-shaped desk, with supports on the ends.
I'm concerned about the elbow area where I would be sitting, since I prefer not to put any additional supports in the leg area.

To add to the weight, I'm also putting a keyboard tray mounted on the bottom of the desktop.

I was thinking of using an aluminum 0.75" x 0.75" x 96" L-support. I would screw this diagonally under the desktop to provide the extra support (maybe run 2 of these).

My desktop is 6' x 6', with a 24" top using 3/4" baltic birch ply. I already have the desk assembled with edge banding, so using a solid wood edge is out.

Is the aluminum support enough? Any other ideas on preventing the sag?

thanks

[Ken Weaver]

I have a similar situation with a sewing unit for the LOML. I was planning on using a strap something to bring the two units together. It think it will be enough as the unit I'm mating to has a sistered top and face-framed.