I believe Keith has used this type of flap which means that his recommendation may be the best way. If memory serves me Al Rabe had the "bump" issue with the Sea Fury and perhaps the Bearcat . I think he fixed it on the Mustang but that was a long time ago and I might be wrong.
If you place the hinge pivot deeper than the radius of the flap LE you will get the "bump". Sealing this type of hinge is not as critical as ones that have a visible gap. Any air deflected through the gap will be directed aft due to the shape of the TE which produced less roll force but I want them sealed anyway if I can.
Ken
Al Rabe, to my knowledge, did not incorporate a recessed hinge line on either of his flaps or his elevators. You may be familiar with the "tests" he performed with different wing sections mounted on the hood of his car, then run up and down a runway and was able to measure the lift created by different airfoils, angles of attack and flap deflections. That is where the airfoil that he used on his Sea Fury and later Mustangs came from. In those tests, he did a "variation" of the airfoil that I used on my the Focke Wulf Ta 152 that placed several times at the Nats and was published in MAN. He intentionally place the pivot point rearward so that the flap LE would rise above the wing TE (yes - a "bump") with the idea that it would at least partially seal the gap when the flap was fully deflected. His findings were that this section did not improve what he was getting with Sea Fury section.
I know for a fact that the "bump" created by the rearward position of the pivot point is definitely NOT a good thing. As the air flows over the wing, by the time it gets to the flap hinge line, that air flow is probably turbulent. When the air flow sees (feels) that "bump", I think the air flow separates and any lift that might be created over the flap is negated, though there is still some resultant lift created from the bottom of the deflected flap.
Why do I believe this? I will try to explain. I built a Rabe Bearcat, essentially from the magazine plans, using the published airfoil for the wing but the wing was built using Bob Hunt's Lost Foam process (meaning it had a molded LE, no LE strip) The stab which was essentially a flat plate with a rounded leading edge. The stab is 3/8" thick and was formed with molded sheet (so there was no LE strip) -- It is just a 1/16" shell with only a few ribs. Based on my experience with these thicker sections where I recess the pivot points for the elevators (and flaps), but that pivot point is about 1/32" forward of the radius center of the LE of the elevators. This means that as the elevator is deflected, the LE of the elevator drops away slightly from the surface of the stabilizer. So far, this is fine. That Bearcat performed very well, particularly when I taped the hinge line with the tape applied as I explain earlier in this thread where the tape is attached to the elevator LE as the LE rotates inside the stab TE. Things are still fine so far and the taped hinge line definitely improved the turning performance of the airplane. The tape is place on the bottom of the stab/elevators hinge line. However, a problem raises its ugly head when oil gets between the tape and the elevator LE. After a number of flights, the tape will loose its adhesion to the bottom TE of the stab and as up elevator is applied, the tape will bulge, creating a "bump", probably no more 1/32" to 1/16" for a few inches extending from the root of the elevators. The turning ability of the Bearcat was definitely impacted. Removing the tape, cleaning the surfaces from oil, replacing the tape and the turning ability returns. I have experienced this with every one of my models where I have recessed the pivot point. Some of these airplanes have flaps and elevators that are as much as 1" thick at the root sections. There is no visible gap between the elevators and stab or the flaps and wing.
That "Bump" is not a good thing and can easily be avoided by careful placement of the pivot points. Placing the hinges on these thick flaps and elevators gets kind of tricky when the flaps and elevators are tapered in thickness.
Hope this makes sense. If your would like to talk about it, send me a message with your phone number.
Keith