Byron's shot of the v-notch in his flav reminded me of a tip - I think it was from British tier Ian Moutter.

When cutting the notch, make it slightly off-center by tilting the upside down fly a little more to the right (for a right hand tier with the eye facing you).

Otherwise the natural curve of the hackle will bring the hackle on the right hand side of the fly (when turned rightside up and eye facing you) orienting downwards while the hackle on the left hand side heads more to the side. If this happens, the fly may not "cock" properly on the water.