RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?
There's certainly no end of suggestions for this one. Seems like a lot of ideas will work. I've never tried this setup for a 2nd. clunk but remember a reply to a similar post a while back. Made some sense if there's concern about the 2 clunks interfering with each other.
Install the 2 clunks by making fill/drain line a little shorter. But, splice a short of brass tubing midway along each clunk line. These 2 lines can be secured side by side. With a piece of fuel line on both ends of the brass slice pieces the tubing and clunks are free to move up and down with virtually no chance of getting tangled with each other.