Folks, believe it or not, yesterday I got a phone call from the technical manager of BMW BeLux. They had indeed taken due note of my complaint, and were going to try to reproduce the problem today.
This afternoon, I got called up again by them. They had put the large topcase on the GT, put in a full BMW raingear and some other junk. Then they'd filled up the sidecases with tools, up to the maximum allowed weight. They took 4 people of various height and weight and asked them to put the following bikes on their centerstand :
R 1150 RT (can't have been the same topcase)
R 1200 RT
K 1200 GT
Their was a consensus that for the same load, the GT while not impossible to do so, was way more difficult to put on its centerstand then the two other tourers. A question of wheelbase and weight distribution they say. Like I hadn't found out.

In any case, after the test, they contacted BMW Germany, who while not minimizing the problem told them they only had gotten three similar complaints.
May I request from any of you who have had the same problem with their GT, to transmit it to your freundliche for further handling ? They might contemplate a similar modification to the centerstand as they did on the GS. I think that the more reports of difficulties come in, the better chance we make of getting the centerstand modified and retrofitted. At least, I know for sure now that I'm not the only case.
Thanks,