Tablet area is strictly preference, I've seen people progress extremely fast with really small, medium, and even full area. Also I'd recommend using OpenTabletDriver for your tablet rather than devocub/hawku drivers.
Not to mention you've already hit your peak rank around half a month ago with this area with a pretty steady improvement graph at the moment.
For example this is my area I've used for about 6 and a half years (although I did change from 1920x1080 to 1680x1050 around a year ago)