Change play previw editor window size to match 1280x800 (android)

How would i set the play preview editor window to fit my android tablet i am developing for?
It has a screen size of 1280x800, how would i do this?
Here is a screencap of the choices i have (which is very limited)

LimitedChoices, This shows a very limited choices of android screen sizes with no way to customize what size you want...

EDIT: I just realized that the mobile platform does not have the standalone option. So try switching to PC/Mac Standalone (File->Build Settings-> Select Pc and Mac Standalone and press switch platform) and then changing the resolution for the player as noted below.
I know this isn’t perfect, since you are not in the mobile platform anymore,

  1. Set the play preview editor window size to ‘Standalone’

  2. Go to Edit > Project Settings > Player

  3. Change “Default Screen Width” and “Default Screen Height” to 1280 x 800.

Good Luck.