Trailing Edge Radii
My 7 drawing 4PP says the elevator trailing edge radius should be 3/32, and that certainly appears to be an outside dimension. Because of metal thickness and springback, a 3/16 diameter dowel magically held in position (dowels will want to squirt out) won't let you get a radius as tight as the drawing calls for. a 1/8 (4/32) diameter dowel should allow you to get there, but over squeezing is bad news. Too tight a radius results in a weak structure, increases the risk of cracking, and makes it more likely you will end up with a crooked trailing edge.
My drawing 5PP shows a radius of 3/32 for both the elevator and rudder (early, bent trailing edge rudders).
My drawing 7PP shows a radius of 1/8 for the same early rudder--Van's can't be accused of making things restrictively consistent for us. I take this to mean they are comfortable with anything between the two numbers, but a call to them would never hurt.
My aileron instructions say to use a radius of 3/32 to 1/8. My aileron drawing seems to show a 1/8 radius.
I made a simple go-no go gauge from a flat piece of aluminum. It has two notches. One notch has a 3/32 apex radius, and the other has a 1/8 radius.
Make sure you have a very flat surface leading up to the trailing edge. Another hint is to make sure your bending brake surface is as flat as possible.