Windows 10 Tablet Resize?

I am looking to get a windows 10 tablet to run HP Tuners in my car. However, where I want to install it only allows for 2/3 of the screen to be shown. What should I be searching for that will allow me to control which pixels are used as the display and to just let the rest stay black? Say I want to run the top 2/3 when the tablet is horizontal, yet have it be scaled properly, just extra wide for that resolution.

Bonus: Whats the best way to have tablet boot straight to HP Tuners and skip as much of the bs as possible? I’m thinking I can use power settings to conserve battery when it’s not receiving power (car ignition turned off, sleep the hard drive, dim the screen) and do a quick wake right to HPT. The end game to this would be to use a raspberry pi or some chip to read the can data and display that directly but this is a stop gap measure until I get the time and desire to work through that. I’ve been using a nexus 7 tablet with a obd bluetooth module but I want a little more functionality than that.