Armin,
I don't think the designers are expecting the size to change out from under them. I'd call it a pretty minor annoyance, feel free to post it to the bug report site, there is a link to it on the Wiki.
>so this seems to be the only way ... Of course it would be nicer to have all changes reflected correctly without having to save the changes first, but after all it's not that bad. I can live with both solutions ... leaving the green rectangle there or save the changes and close and reopen the designer.
>
>So this could be considered a minor bug ...