Use a nickel to spread the lower portion of the clamp.
Check out the Xtracycle Blog for a useful tip on installing Watchamacolars on a Big Dummy. Since the tubing of the Surly Big Dummy is larger than the Xtracycle sub-frame the lower portion of the Watchamacollars is a very tight fit. By using a nickel to spread the lower part of the clamp you can get it on much easier.
Good tip!…=-)
The Lazy Rando Blog... 
Great tip! This trick has really helped a few of our customers.
I posted a link to this on our Whatchamacollar listing.
http://www.biketrailershop.com/xtracycle-whatchamacollars-rack-mounts-p-1435.html
Thanks for being a great resource!
Robin
http://www.biketrailershop,com
Yes, good tip! (also works for seatpost clamps integrated into frames).
But here’s the problem I’ve got with the Whatchamacolars related to U-Tubes… The U-Tubes are a huge improvement on the older style wideloaders, which were way too wide, too blunt on the leading edge (hitting an obstacle with one would be dangerous), and the cloth panel was necessary without being very useful. BUT, the U-Tubes rattle like crazy on the Big Dummy frame. I’m not thrilled about spending $25 extra on an extra pair of Whatchamacolars to fix the problem, but I would do it, except that they won’t fit on the tiny bit of horizontal frame-tube on the back of the Big Dummy frame (at least from the production year I have) so the WCollars won’t fit! I can’t use a pair on the front because I’m using a kickback kickstand (which I also like a great deal).
I’m wondering if I used heat-shrink tubing on the U-Tubes before I inserted them I might be able to get a snug and quite fit. Any other ideas?