After getting back from a trip to Tennesse and the Honda Hoot, I finally got around to washing and polishing up my bike. I bought some rim trim at the Hoot and put that on, then took off for Curves and Karate. I thought the trim look terrific, so when I got home I asked my husband to take the bike down the street so I could see what it looked like in motion, and as he went behind the bike he spotted a screw in the back tire. We don't know how long it was, and the head was a sticking out a bit, like I'd just picked it up on our street or driveway.
Long story short, my bike's getting two new tires. Guess it's good for me that I've got about 7000 miles on those tires. (The front tire was cupping anyway.)
Anyway, my vote is to be very cautious about plugging the tire.