Hello Pops
Love the new red bird, but you don't need no flaps to make that thing land short ;-)!!!!
Ok, so for a cub, what you get is a plain flap, so all you are doing when you pull on the flap lever is increasing the camber of the airfoil (like all flaps)... Piper's design was not intended to perform like a slotted flap albeit, what you got was some extra airflow over the flap, and that hit the tail and made it shake, thus the flap gap was born, to reduce that turbulent airflow that hit the tail.
On a given cub, test the with or without the flap gap, and you should see very similar performance for the same bird... (albeit you are making it more draggy with out it, and it could be a desired attribute for STOL but you get the hakes and it is not too comfortable)
Moving on, what I have been considering is building a slotted flap... here is the tested numbers vs normal flaps.
As you can see, a plain flap gives you two things, better Cl at a given alpha (AoA) and retarding airflow separation.
I came across this interesting graph, I am posting it for argument sake ( I have not verified these numbers but it looks fairly close)...
I believe you are shooting for a blown flap, but you will need a jet for that...
A true slotted flap would keep performance at cruising while getting you ~80% increase in Cl_max at a lower alpha (AoA) IMHO, but you would need a new wing for that, not something you can easily bolt on, that is what I am working on... some progress but I made the error and effort in working on Carbon and that is $$$ and Slow...