After more trial and error with different Corvette loadouts, I've settled on this one:
http://coriolis.io/outfit/federal_corve ... ck%20Widow
Two huge cannons and a mix of pulses and beams. I put beams on the small hardpoints to maximise their usefulness as they stay on target most of the time, while the large hardpoint spends a lot of time off-target because of its bad position on the bottom.
Edit: small gimballed beams, not fixed beams!