I'm planning on building a new workbench (actually I was planning on this a few years ago and got sidetracked but we won't talk about that right now). It's a based on a couple of simple designs but essentially, I was planning on trestle legs with upper and lower stretchers, using mortise and tenons on all the joints. I've decided to forgo my original plan of laminated top and use 3 or 4 layers of MDF with a hardboard top for a variety of reasons. I plan to band it, though I haven't decided with what yet. However, since I'm planning on making it 8 feet long, I figure the MDF will likely sag in the middle. So what's the best way to support it along it's length?