Squaring C-Beam with a Mill

I'm preparing to square all of the extrusions for my C-Beam XL build, and I'm wondering if I can just load the extrusions one by one into a vise on my CNC Mill and run an endmill along the ends of the machine. The real question is this: am I going to damage the extrusions by clamping them down nice and tight in a 3 inch vise? I don't know how strong the extrusions are and don't want to bend them or crush them so the v-slot wheels don't run properly.


Thanks