A spare tablet can give fuel, relative gaps, or pit information a place of its own. Start by noticing what you already look for during a run. If you routinely open a menu to check fuel near the end of a stint, put fuel on the dash first. That gives you a clear way to judge the extra screen.
Set up one readable screen
Check that the dashboard app supports your simulator and device. Make the few values you use big enough to read from the seat and give each one a fixed spot. Choose one screen for driving and save detailed tire or lap charts for the garage if you use them there. Try the brightness in the room lighting you actually race with. A bright display near a dark main screen can keep catching your eye.
Check it with the wheel installed
Temporarily hold the tablet where you plan to mount it, then look through the wheel and over the rim. Check the view in your normal driving posture with the wheel at different angles and the base off. Leave room to remove the tablet, use its connector, and move past the bracket when you get out. Compare the tablet’s dimensions with the fit range on any tablet mount you consider, including the case if you plan to leave it on.
On the next solo run, glance at the tablet on a straight and see whether you can get the information in one look. After the run, remove anything you never used. If a reading still makes you hunt, give it more space or move it back to the garage screen.