{Lifting airfoils are designed to have the upper surface longer than the bottom.} This is not always correct. The symmetric airfoil in our experiment generates plenty of lift and its upper surface is the same length as the lower surface. Think of a paper airplane. Its airfoil is a flat plate --> top and bottom exactly the same length and shape and yet they fly just fine.
At last.
I remember as a 10 year old boy reading the theory of lift in textbooks and not believing a word of it - for the very reason mentioned above.
All through my life I have stuck to the published theories and spouted them verbatim - still not believing a word of it.
As an aeromodeller - how did my simple glider with a flat plate section create lift, how did my aerobatic model with a fully symmetrical section fly?
Air cadet - the same.
Then as a pilot passing all my exams (with 100% - but not believing the theory to be the truth!)
Now, at last the mystery is resolved.
Nice to have a scientific answer at last.
... now haven't the 'scientists' 'proved' a bumblebee can't fly ... ?