It is a little tighter around the ebrake and mufflers, but i've never had a cat-back that had any issues with the shaft and my ebrake (although it doesn't work) doesn't rub.
Like i was saying before though, i think any advantage that it might give you in weight savings is going to be lost because of its larger diameter. I can't think of the term for it but spinning objects with a larger diameter consume more energy than smaller objects. It's really only 5lbs or so lighter too so the biggest reason to get one is the vibration thing and the fact that they're much stronger. I've heard that the shaft itself will handle 1000ft/lb if you have the universals that'll take it.
Are these the aluminum drive shafts coming out of the vans or are you guys buying these new? I'm getting some serious wobble and its becoming apparent at lower and lower speeds, I think I'm gonna putt off the dogbone cause it looks loose.