Does anyone have any experience modifying a normal fork-mount Yakima tray for tandem use?

I'm planning to bolt a beam to the tray that will extend 80 inches back and lift the rear wheel 2 inches. Using a board to site from the fork dropouts to the rear wheel, it will clear the front BB shell without raising the rear. I'll then bolt a short tray to this beam and strap the rear on there.

When I bought my bike used, I just rested the front chainring in the Yak tray, clamped the fork in, then used one of those ratchet straps to pull the top tube down and force the fork into the QR. I don't like that for repeated use, but it did work fine. No movement with a 30-mile road trip.

Thanks!