You can't compare a photo of the left side vent on #07R with the right side vent on #11R. All the short tailed GTRs have a small vent in the left side luggage door and a larger vent (identical to the one in the #11R photo) in the right side luggage door. Here is a shot of the opposite side of #07R showing the larger vent which feeds air to the oil cooler.
That said, you've made other convincing arguments and I'm not against believing that AMG used #11R instead of #07R. Things that are in conflict with that hypothesis are (as you mentioned) that DA mentions #07R was the car they used, and also one of the first ads that appeared online for #07R (we're talking 3 years ago) also made mention of the use by AMG in development of the CLK-GTR as I recall.
Some of the other details you point to could have easily been add-ons to #07R. There's nothing that I can see which makes me 100% convinced that this has to be a 1996 GTR. I really wish there was so we could put the discussion to rest.
One thing that might add some additional credibility to the #11R theory would be the date of the AutoSport magazine article you posted. Depending on when that was reported, it could actually rule out #11R (and most other '96 GTRs) since it would have still been competing in the 1996 BPR Global GT series up until November 1996 at the last race in Zhuhai, China. If that article was printed prior to January 1997 that would cast a big doubt on the possibility of #11R having been the chassis that was used.
>8^)
ER