Imagine driving the fiberglass over tube frame Porsche 917 at Spa, Le Mans, Daytona, Sebring, etc
at over 200 MPH
on the Mulsanne Straight (when it was still straight)
in heavy traffic filled with slower cars (and amateur drivers)
in pouring rain
on bias ply tires
with hand carved rain grooves
a) fiberglass over ALUMINUM tube frame P 917,...
b) almost 240 MPH on Mulsanne
They used compressed gas in the aluminum tube frame to detect weld failures.
They would check the held air pressure every 4 hours in race conditions to see if the frame was coming apart.