Skywave.
Agree with you. When I flew out of Luton (in a PA-28) most of my departs were from Charlie.
The point (as I am sure you know better than I) is just to never wish you had used more runway or carried more fuel .... it's part of the safety "calculation"
The old adages I used must have a cut-off somewhere. The point is perhaps not to have too little runway ahead or to have left too much fuel behind.
You are right about Full Lengths and Full Tanks
DGG