Let me 'splain a little better about "spoilers". Those are control surfaces or wing features that can be changed in flight - as in on final approach to reduce lift. What you are doing by manually adjusting the aileron linkage is a more permanent adjustment. Always do such things small increments. If you raise them enough to create turbulance you may find them tearing away from the wing at higher speeds. That is ALWAYS a bad thing.

Think about what is going on. By lifting both of the ailerons you have changed the chord of the wing. It has a similar effect to decreasing the angle of incedence/attack of the wing - thereby reducing lift.

Another way to slow a floating model for landing is to drop to a prop with less pitch. This adds some drag at idle speed. Like downshifting in a car and using the engine for braking effect.

You're into one of the joys of modeling now: futzing. Making adjustments and changes that effect the way a model behaves. But again, I recomend small changes and make them one-at-a-time so you can see better the effect. Aad remember: 50% of changes make things worse. That's simple statistics and the primary reason to make small changes.