If you choose "maximize" in the upper right corner of the Remote Assistant screen, it should only maximize enough so it fills as much of the screen as possible without requiring scrolling on the remote screen to see everything.
If you want an example of one that works correctly, try to Maximize screen of TeamViewer. It asjusts the screen pixels and percent of zoom so that the whole remote window shows without having to scroll to see everything.
Thank you for suggesting this awesome feature, we are currently remodeling the screen and resolution calculation mechanism, so it is subject to change and after it is stable and works as intended we will think about this feature. I have created a feature-request anyway, thank you.