What your looking for is a clean,smooth transistion from the mast to the sail.

On the beach sheet your main like your going to weather. Make sure the mast is rotated fully. Look at the sail-mast junction. It should transistion smoothly. If it looks under rotated, file the stops until sail-mast junction looks perfect.

This will give you max. power and the least drag. Different sails may need different angles of rotation. So don't go crazy filing.