This has been pretty well covered, but briefly - TOM has a 12" radius. The W compound radius works itself out to around 18" at the bridge. In practice, it's not a huge deal, in fact the differences are a bit hard to see with the naked eye. The net effect is that your middle strings have a little higher action in the upper frets. Some people dont do anything about it. others, including me, file the bridge saddles down in the middle to approximate an 18" radius. A little filing goes a long way. You want a triangular file from any hardware store and a good 18" radius gauge, either homemade or the stew mac kind, plus a tiny file like a .010 nut file to re-notch the saddles grooves, and something to smooth it all down and get rid of the burs when youre done.