ORIGINAL: FHHuber
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.