V2 of my first design (https://www.thingiverse.com/thing:2966479) to remove all issues with that one:
no fixation for the heatbed cable - now integrated
still some flexibility - now with 20mm height this thing doesn't flex, which improved my ghosting with small fast prints.
I printed with carbon filled PETG but I assume it will be as solid with normal PETG due to the height.
Total weight with 4 walls, 15% gyroid infill: 195g
BED hole position: 210 x 210mm
Formfutura Carbon filled PETG
Can be printed without supports.