I use a piece of 3mm dyneema which goes through the little holes in the middle of both boards, tied with a figure 8 on the back side, and running across the tramp. I leave just enough slack to make one wrap around my fist, when both boards are fully down.

I race alone usually, so it really helps me to get the low side board up if needed, without having to go down there and grab it. Even when racing two up, it's much quicker for the crew to just grab the line and give it a good yank and the low board will pop right up, at least half way, without having to crawl under the boom and try to lift it.

Also, when coming ashore, it's easier and quicker to get them both up.