I understand your question, but I recommend, carrying a
hand pump to pump out water. I had my kayak fill up with H20, because the end caps on my flushmounts slipped off, I assumed that they were glued on tight. I was about 3/4 mile from the Islander, and had about 1/2 my kayak full of water. It becomes very difficult to paddle, and very, very tippy, with each paddle stroke. I had to have my legs over the side, which slowed things down. I finally had to call the zodiac tender to come pick me up. If I had that happen inshore, with no pump, I'd head straight to shore, anywhere. Or call Mission Bay Life Guard, who responds to La Jolla. So to answer your question, I think it would be hard to tow a sinking kayak with another kayak.
chris