[McGillicuddy]

I think you've done a real nice and safe job of setting up. Regarding the spread, you may still want to consider notching a couple of 8' 2x4s and maybe a 10'er and lay them across the beam with notches over the open gunwale at a few spots just to be sure. Certainly wont hurt..

Strick or someone else might have a better sense of if it's necessary. Figure the boat's in its working place and since you know the potential for said side sag exists, why not counter now, especially if the project might take a while?