You're my hero of the week for doing this!

Some seriously nice results you've got there so far. I was a bit dubious that slotted flaps would work at all for our model size. But from the sounds of it you're clearly seeing it work with great success.

A flap that redirects the air such as this will greatly increase the achievable lift coefficient for a given size wing and be a big advantage in models where we want to achieve a very wide speed range to allow blistering fast speeds but still slow down to acceptable landing and takeoff speeds. And since size counts when it comes to high speed drag being able to make a smaller model with the same size jet turbine or EDF means the high speed can be higher. Yet with the lift you'd get from flaps that can maintain directed flow you can safely go smaller and still get the lift at regular landing speeds to allow the use of a smaller wing and model.