Good heavy duty switches are hard to come by. Stop by your local small engine repair shop and have them order you some chain saw switches...chances are they won't have any in stock because they never fail. They will utilize a screw terminal instead of spade connectors.
!0-4 on the relays...make a world of difference. Quality stuff here...
http://www.leashelectronics.com/
Good reading/advice here...
http://www.madelectrical.com/electrical-tech.shtml