I had one for a while in my '69 and, like Jim, I pulled it out when I realized that it was holding moisture under it. I had a slight leak around one of the tail-lights that didn't amount to much but with the mat there it couldn't dry out.
OK, mine is also. How do you like the urethane? Mine is just a cruiser, I am not looking to improve handling but would consider urethane if ti is an "upgrade over the stock rubber in terms of ride quality.