should the hard chines be left on a stripper as an angle, such as the Petrel or do they get rounded over when you sand the hull.

If a chine is meant to be hard it should be left fairly sharp, however, the sharper and angle is the more delicate it is. You want at least a 1/8" radius to allow the glass to conform and too keep the edge more rugged.

Sharp feature lines above the waterline can get away with sharper edges as they are less likely to take a hard hit.