Using the designer on a 7" screen I have a hard time adjusting the views graphically. Usually takes several attempts to grab the handles. Sometimes I just give up and type in number values or just opt to do it dramatically.
Do others have this problem? Screen sensitivity, fat fingers??
Maybe if the red box handles where bigger?
Also I can never drag the bottom of the red box flush to the bottom of the screen.
Assuming you working directly on the device,
for this type of operations I suggest to get a pen/stylus. there are pen on the market which wold work on this type of screen (I had one, but I lost it). I plan the get the new one anyway, because I really liked it for some type of operations.
I recommend you to work with the emulator when working with the designer. You can create an emulator with the screen size of your tablet: Creating emulators for large screen devices