Right, resizing is highly disorienting and doesn't allow incremental adjustments.
In the long term, I want a better resizing dialog. And it would be really nice to focus the camera on the change.
Here's a short-term fix to ease the pain: When we resize the map in the editor, the camera will zoom out as far as necessary to view at least the entire map. This is usually as far out as possible.
This fix is alrleady on unstable's master branch. It's planned to go in the next release.
-- Simon