The best place to go for rigging/sailing tips on 420's would probably be their website. http://www.club420.org/PAGES/Library...uningGuide.pdf
for club 420's. The International 420's also have a US site with a discussion board:- US I-420 Association
, but it doesn't look too busy. The club site mentions how the mast rake affects the jib lead angle, which is apparently important. Overall, increased rake would help move your center of effort aft, and to some extent lower. In heavier air this might be helpful to keep the boat pointing while sailing flatter. In lighter air, less rake could help provide more drive in the sail to push through waves. The 420 sites will have more specific input as to why you'd want one or the other, and how much of each in varying conditions.