Its not just the Tail boom its the engines too they take 1 ping and they stop working. 
Here is a list of damage I have taken in the past 12 sorties in the P38.
  1- both engines killed- ditch ( a total of 2 shots hit me 1 in each engine)
  2- Tail boom shot off (1 ping)
  3- Tail boom shot off (1 ping)
  4- Tail boom shot off (1 ping)
  5- Tail boom shot off (1 ping)
  6- 1 stabalizer shot off and 1 engine and a gear hit- Landed (18 shots from ground fire)  
  7- Tail boom shot off (1ping)
  8- Tail boom shot off (1 ping) 
  9- Tail Boom shot off (1 ping)
  10- Radiator hit- RTB (1 ping)
  11- both engine killed and TAIL BOOM SHOT OFF (5 pings)  

  12- augered fighting a Spit 9 ( I was afraid my tail boomb would get shot off)  

                         Hodo