"...Going 20 under (55 in a 75) is just as dangerous as 20 over. ..."
But common sense must prevail.
Often folks in a hurry or excited about vacation will use the excuse "...keeping up with traffic .." To drive 70 and faster - pulling a camper with ST tires rated for a MAXIMUM of 65 MPH and on the next trip are reporting on here that their "China Bombs" exploded and ripped the side off their camper-all the while not knowing they set the stage for that by "..keeping up with traffic.." And started the separation process then.
If common sense does not prevail,Murphy's Law certainly will.
Drive a reasonable,safe speed and don't worry about things you can't control.