Advice on positioning boat on camper roof please!

Y'all made me look it up. It's 4' past the tail lights requiring a flag in CA at least. It's good to keep things like this in mind.

I think that I will get a retro-style foam block canoe rack to hook onto the camper roof as a third tiedown point in addition to the factory bars which are poitioned toward the rear. Any obvious flaws with that line of thinking?

I do have the ratcheting bow and stern tiedowns. We needed those to be easy so that we can pop up fast. :)