If you want to experiment with wing tips, make the end of your wing flat with a ply or thick balsa rib. Then you can bolt or screw on end plates of various types.

I have done this numerous times and have published it and have had readers of my column duplicate the experiment. End plates for a Falcon 56 sized plane need to be about a 1/2-3/4" extension all around the wing.

Plates will increase the roll rate, lower the stall speed, lower the landing speed, tighten up your loops and maneuvers and also make good skids if you tip over.

Lower only end plates act like anhedral and will reduce or eleminate the roll due to rudder in high wing planes. I have done this experiment before, but am doing it again, hopefully, this weekend or the next, for my column. You make a lower plate that extends down about 1 1/2 inches. Fly and put in rudder and check for roll. The plane should roll backwards, right rudder-left roll. This indicates plates extending too far down. Trim off in 1/4" increments until you kill the roll due to rudder. This one is really easy to do with a SPAD (Coroplast) plane. You just carry some utility shears to the field, fly & trim.

For STOL, you need to use flaps or flaperons. With big plates-try an inch and a half all the way around-and flaperons, you are trapping a bunch of air under the wing when you go full power. I like to hold full up, giving full down flaperons, and hit full power. A light plane can literally levitate into the air. You might also need to add another inch or so to the flap (inboard) section of your ailerons.