It was quite a learning experience for new Co-Pilots.  Also for me the first 
time.  It would not have been so safe except for the hot wings and tail. 
Perish the thought if a heater had gone out.
These rubber boots on wings, to me,  are a far cry from the old DC-6.  I flew 
the DC-4 for several thousand hours with rubber boots and it was a constant
effort to keep track of conditions.  Bob Buck who was the head of Training 
or
TWA said it about right.  He said something like,  "not to effective but does 
keep you busy" or words to that affect.  Maybe you have read his book.
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