Switches and turnouts

The Oil Czar-Jerry H. and I were recently discussing our mutual ignorance of what makes a switch or is it properly a turnout a certain #. For example I beleive some of our switches on the SVRy are either #4's or #5's. I know that this relates to the radius of the turnout ie. how far you go for the tracks to diverge, but how can you tell what switch assy you have. Some of our swithches are a bit tight for 19's ridged frame length and firebox modifications prevent the trailing truck from having as much movement from side to side. Our roadmaster is looking at changeing out some of our swithces to alleviate this problem. What sort of guidelines can some of you old hands give as to how you would determine the minimum size switch required. What size are the switches on the C&TS. What degree are the sharpest curves on the C&TS.