I find myself making many objects out of 3/16" flat plate. Usually I like to setup the machine to make a few objects in the same run, because I can pack them together to save material and spend less time setting up raw stock on the machine.
I'm having a hard time finding a good way to hold down larger sheets of plate. Yesterday I run an operation on a 3.5" x 9" x 3/16" piece of 6061. I held it down with this sort of clamp:
The clamps are 9" apart, at the far ends of the stock. This makes the stock bow up in the middle, making it hard to get accurate depth of cut. The middle is also not well supported and vibrates easily.
I'm wondering if using two toolmakers vises side by side would be a better option? I have one of them, but could get another. That would work well if I didn't use the full width of the material (I often do).
What other options work well?