I tried other materials, but it only seems appropriate to print improvements for your printer.
The slop of the printing surface is horrible because the screws with springs on them for adjusting the height are 3mm and the holes they go into are 4.6mm. These are called "shoulder washers" elsewhere, and you can probably get them somewhere else. But I measured and printed them out to try them. No more slop!
I wish everything was this easy.
Providing the OpenSCAD source files in case your need is different.