The idea of using slow flying aircrafts for ground attacks have been tested with surprisingly good results. "dont get low and slow unless you get really low and slow" is a good rule. The Po-2 is another good example.
The concept was also tried successfully in the late 60:s

top speed of ~90 mph but they managed to destroy a number of MiG-17 and IL-28:s with only one shot down by flak, The MiG-17 where way to fast so the pilots often fly right by them without spotting them.