Dago:

When the P-80 (F-80) was developed into the T-33 it had a bad characteristic: control departure often put you in the grip of what was called "TheThing." Guess what.

On the T-bird this was solved by adding empennage area. Logic tells me it was added to the vertical fin, but memory says it was added to the horizontal stab.

but on a small plane it's eay to try, and hurts nothing.

Cut a triangle of medium balsa, fit it to the front of the vert fin, make it look like a P-51d. Stick it on with Shoo-Goo or something else that will come off when you want it to. Fly it. Improvement? Make one a little bit larger and try again. When you stop getting improvement, do the same triangle trick to the stab. You will find a combination that will work fine. Might take several tries.

When it flies as you want it, then make nice parts to go where your temporary ones were, glue them in properly and paint/cover them. Fly happily.

Twin caught in "The Thing? Either get out, or "Ka-Ching!

Bill.