Amazon Fire HD8, Can't get full screen resolution

I'm clearly doing something wrong but I can't figure it out.

I have an Amazon Fire HD8 with a screen resolution of 12800x800 but when I try to set the root geometry to those dimensions, I get scroll bars in fullscreen mode. The best I can get is 960x580, I've tried with both the built-in Silk browser and also with Full Kiosk Browser.

Any ideas?

Besides changing the zoom there's not much to do about it, open stage control uses what the browser provides. It's very likely that the actual resolution exposed to the browser is smaller due the device's pixel ratio (see https://www.whatismyscreenresolution.org/). In any case, I recommend using a combnation of vertical and horizontal containers instead with the default fullsize root to create a layout that scales with the screen size instead of setting a fixed root size.

Thank you! I appreciate you taking the time to answer my newbie questions. That website is very helpful. Yes, the screen resolution reports as 962x601 while the device resolution is 1281x801 with a DPR of ~1.33. The browser viewport reports as 962x602. I need to read more about that.