final update: I bought the prototype from a shop; tried it out on both
sides of my Surly, and -- well -- HATED it. For the life of me, after
watching numerous videos and getting tips from the Xtracycle web site
and trying different tightnesses of the stem clamps, and no matter what I
did the thing just made my Surly wobbly as hell. Didn't matter if it
was loaded or empty, it was completely unwieldy to steer and even after a
week of trying to get used to it I still ran into stuff.
Talking to several folks who'd tried sidecars, the responses ran to
extremes: they either loved it or hated it and there really wasn't any
in-between. Looks like I was in the I-hate-it camp. So this morning I
put it up on craigslist. I got five responses within two hours (of
course I did; shops don't carry these much and Xtracycle seems not to always
have them on hand), and by dinner time I had sold it for my asking price to the first guy who
responded. He was firmly in the I-love-it category, and I wasn't out any money when it was over.
I'll go back to using the Wideloaders and trying not to overload the bike. Probably the guitar and mic stand and cables will go on one side and the amp on the other side, or something like that. The other grand ide is to figure out a way to hook up a trailer to the back of the Surly, which will make for a stupid-long vehicle but might be worth a try for those rare, really big loads.