The best thing about a plate is that it makes access easier for things like removing the router and for bit changes. I have a router extension on my table saw without a plate, so access is a bugger. I ended up just having a dedicated router that I don't remove, and putup with the extra effort of bit replacement. The extra supports on the corian sound like they should work. Just keep in mind the variety of sizes in bits that you may use. 1/4" strait bit on small projects, or a large raised panel bit, will either be hindered without a plate or removable bushings?