I flew a Goldberg Cub that belonged to a fellow flying buddy for it's first flights. His had the same OS .60 on it as you mentioned The model is already overpowered with the .60 so I don't see how putting a .90 on it will make it any easier to land.

Flaperons on standard ailerons is a REALLY bad idea. Deflecting them down also adds the wrong sort of aerodynamic twist to the wing so the risk of tip stalling becomes VERY high. And if it tip stalls low to the ground you will end up crashing for sure. The proper way to deflect the ailerons to aid in landing is to deflect them UP. Then they are known as Spoilerons. Deflecting them up produces washout in the wing and makes the tips less prone to stalling so the landing approach will be safer.

But either way this is a lightly built model with lots of wing area. Even with the spoilerons angled up 60 degrees the drag added will be fairly minimal. In my buddy's model's case the engine power even at idle was enough to make it all but impossible to land. THe proper method of raising the nose to get the glide speed slower and raise the wing's angle of attack where it's more draggy just resulted in the model "gliding uphill" even at idle. I found that the only way to get the darn thing to land was to line it up and then actually shut the engine down and land dead stick.

For taking off I never did reach full throttle before it lifted off. I advance the throttle slowly so I can deal with any veering off by adding rudder. And even with moving the throttle towards full over a couple of seconds the model was always airborn by the time I was at about 1/3 throttle. After seeing how it flew he took it home and put a .40 into it. I never saw the plane again but he showed up one evening with another model and in talking with him he said the .40 was still easy to take off and climbed at a high angle at good speed but now the model actually could land fairly easy at idle.

It was the sort of model that if the pilot found himself in a thermal I don't doubt that he could shut down the engine and soar with it.

So I sit here aghast at the idea of this same airplane with a .90 on the nose. You really do have the wrong airplane for this. Or perhaps it's the airplane has the wrong owner.... Either way, with a .90 on the nose even with spoilerons you won't get it to land with the engine running. There will still be enough power at idle to actually climb at a shallow angle And I doubt that spoilerons will ruin the wing's lift enough to make a big difference on this count.