I've had the same Shad set for 4 years now.
You're right about the width, with panniers mounted the sucker is as wide as Goldwing - but the space is amazing. Took the missus through Holland, Belgie, France, Switzerland, Italy (Garda/Venice/Dolomites) and over the Stelvio Pass for good measure - then back via Cherbourg. She had the panniers and all my stuff, plus lube/tools went in the cavernous topbox.
Fitting was straightforward and the pannier rails aren't obtrusive - so they stay on. You have to remove the indicators. Can't fault 'em and real happy. You can get two helmets into the 48l topbox - real useful if you have a mate on a sports bike, as he can dump his in there as well.
Only criticism is the mounting plate paint finish blistered and rusted (stessing I guess). Whipped it off, wire brush, primer, Hammerlite. Crap paint job - but its the underside & you can't see it.
Well happy otherwise and great price.