I think it does make a difference, but I would be hard-pressed to prove it. I toured last year, started out with a bob. I weigh about 115. The bob was sort of ok with "normal" load - my tour partner was carrying more of our shared stuff than I was - but it tended to wobble at higher speeds, down hill. I'm talking, like over 15 mph, which is way too slow for a speed limit. On days that it was heavily loaded, it didn't behave well at all downhill. I actually crashed it, it had about 15 more pounds in it than usual because of a long day w/no water on the route. I was going downhill about 25-30mph (too fast) and it tried to overtake me, making me weave in bigger and bigger arcs side to side. End result - I high-sided. After that my partner and i traded his racks for the bob, but he didn't like it either - he weighs about 205. He had a little of the swoopy-wobbly feeling, but was able to control it. So... end result, bob got evicted from the tour, replaced by front and rear panniers, which I like MUCH better - the bike just feels like a heavy bike, instead of the weird hadling I had with the trailer.
This story doesn't really answer your question, and I don't know what the gross weight was in it, either.