My daughters bike constantly fell over when in kickstand mode. The kickstand was a little bit too low for the bike to stand firmly so I designed a higher foot for a firmer stand of the bike. And (at leas for my daughters bike) to my surprise it works like a charm. It makes the kickstand about 15mm longer
I printed it in polypropyleen (PP) for good wear resistance and for it being more or less impossible to break. As a bonus it's surprisingly grippy, even on smooth polished concrete.
Do not print this in PLA, ABS or even ASA. It will break. If you don't have any PP filament, use a hard TPU, that should also be strong enough.
The hole for the kickstand is 12,8mm wide and 30mm's deep. After those 30mm of hole, there's about 20mm of meat