Is SI or SE better for Corsairs?

The 7% and 5.5% was correct on Cannon. The damage output looks something like this for 1 minute of cannon firing. (no bullseye in these calculations)

Normal - 144,400%
w/S.E. - 152,380%
w/S.I. - 155,040%
SI+SE - 163,608%

now check out Rapidfire just for comparison (SI has no effect)

Normal - 80,000%
w/S.E. - 90,500%