it's been quite a while, but I used to work for a plastic sheet distributor/fabricator. I'm thinking we would have preferred to cut the blank on a table saw with an appropriate saw blade (don't recall the TPI, but you should be able to find that). Routers had trouble with acrylic that thick, being so brittle at the edges. Sounds like ballistic grade, is it solid acrylic, or laminated with glass or polycarbonate? How "rounded" is it? Just at the corners? Either way, if you decide to route it, you could possibly get a nice edge by clamping wood or softer plastic on bottom and top to protect the edge corners, this usually helped with any fabrication of acrylic if I recall.
One last question, how far in from the edge will the other plastic cover your piece? the chips I'm referring too are usually quite small.