Some forget that the "modern" regs did not exist when most of our aircraft got their type certification in the old and forgotten days.
There are quite a few with a placard "Slips with flaps prohibited".
Anybody trying to sideslip a Jodel with flaps might be in for some nice tumbling if they don't keep the speed high. (They flick around like clockwork if you go too slow.)
Another one is a Morane with flaps and slots out? Oh boy. Better have some altitude and fresh under ware ready. LOL.