There's an insert for Startups hosted on Thingiverse that works great but for the fact that it's just a little too big for my box.
https://www.thingiverse.com/thing:5197110
If you're in the same boat, then you can try this one.
I keep the English rulebook in the box, and threw away the other one. I also keep it under the insert. I might try a bit more adjustment, but I think we're talking less-than-a-millimeter clearance here, and it's probably not worth the effort to get down the barely perceptible lid lift.
The author remixed this model.
This is scaled down by a few millimeters in order to fit my size of box.