GScholz is correct
It comes down to your deffinition of tough. Surviving 2 - 4 20mm hits may seem tough but in AH unless those 2 or 4 hits are concentrated on a wing tip, cockpit (pk), eng, or control surface I doudt they would cause any noticable damage. If we were knocking jugs down in ah with 2 20mm you bet you would hear on the bbs.
Also you cant make a determination of toughness jus tby examining the aircraft that made it back. It would entail examining all the aircraft (those lost and those that made it back).
A few miracle examples prove nothing. Who is to say that some (a few or many) were lost to fewer hits? It would entail recovering the wreckage and examining it in detail.
No study like that has been done or could of been. Atleast to the point where one could say absolutely that aircraft A is a tank. No plane was ever a "tank". All of could be shot down and were.
The recommended tactics to adopt when attacking an enemy airplane are to deliver an attack at high speed and then break away downwards or in the opersite direction of the enemy line of flight as quickly as posible."while zoom-climbing back to altitude gave the P47 a boost, as the momentum of the zoom wore off, the P47C's acknowledged poor rate of climb returned".
Nothing remarkable here. Most planes flew at a cruise setting. Coming in high and fast then blowing through keeping your energy up would be enough to out zoom almost any plane. Some one posted a comparison report on the p47c vrs the 190a3 or 4 (dont remeber). If you read that you wouldnt wanna fly the p47c any other way.