I've looked but can't find this measurement anywhere....and I'm assuming that this is the part of the exhaust where slip-ons would be fitted to. Correct?

For future reference, where could I find data like this easily? Thanks.

http://ducatimonsterworldwide.org/index.php?topic=4026.0

apparently it is debatable.... well, the benefits of larger pipe dia, anyway.

slip-ons for the small crank bikes are pretty much all there is out there, at least in the off-the-shelf variety

Read that thread...interesting.

The more I look at my bike the more I dislike the way the low mount exhausts are situated. I'm thinking a much shorter exhaust (possibly a small inexpensive conical slip-on) would expose the rear wheel more and give the bike a cleaner look. There's a number of smaller pipes like this listed on ebay. but I have no idea how close of a fit they would be because I don't know the diameter of my mid-pipe. I willing to bet most of these pipes won't just bolt on, rather a little retro fitting will be necessary...