I witnessed my friend's .40 U-C-Do horizontal stabilizer break at moderate speed, straight and level following medium size loop pullout; his engine was Magnum .91 four stroke. There were no flying wires. The built up joints seemed to be poorly glued; it broke at the trailing edge, followed the angled piece outward and broke at the leading edge joint too.

Putting flying wires on the tail might prevent yours from doing the same.

Good luck.
Bob

LOL... a .91 four-stroke on a .40 size plane... he deserved to have the stab break. That is just plain EXCESSIVE overpowering.

It all depends on the plane.
Remember the 56" span Global/Modeltech P47? That was a .40 sized model, but the recommended 4-stroke was .70-.91.
Mine flew like a brick with the .91. It was fast enough once in the air, but had zero vertical pull and took a lot of runway.

This was the case with an 11x10.25 4-blade Bolly (and I expected nothing but speed), but also with a 14x6.

Well... that particular model was a flying brick no matter what you put on it. How it ever got flight tested and approved I got no idea. (but then a lot of the early ARFs were flying bricks...)

The modern models... and the modern (higher power for the displacement than just 5 years ago) four strokes... That .91 on that model is just asking to have parts fly off.

Hi FH Huber;
Apparently, many fliers successfully put .91 4-str on .40 size planes including the fragile U-C-Do. Last weekend there were two Pacific Aeromodel P-51 .40 size at our field; both ownmers told me of people putting 1.20 4-str on them and racing without failure. I wouldn't say anyone deserves to break their plane for experimenting.
Bob

91. 4 stroke on a 40. dont match.