Spoilers Used on full scale sailplanes are not normally at all like what most modelers call flaperons.

Mid chord spoilers do not impart much pitching moment like trailing edge surfaces that reflex up.

What that means is mid chord spoilers cause virtually no tendency to dive or climb on deployment. The airplane will remain in the same attitude but just lose altitude at great rate. Trailing edge surfaces when used as spoilers will demonstrate pitch changes and the need to retrim.

Here is my original Quad Kaydet (it was lost on flight 29 to a midair) and you can see mid chord spoilers that I built into the airplane just for kicks. The results were rather dramatic, when deployed from level flight power at cruse the airplane would remain in the same but be falling flat at a very alarming rate and when retracted would instantly be right back at cruse with not pitch change instantly. There was no real purpose to then and it was just for fun, shock and awe. I did not set them up to function differentially as the airplane roll control was/is excellent. QK #2 was soon flying but I did not bother with the spoilers.

If one build mid chord spoilers they should always be inboard of the ailerons. The last thing one would want is to disturb the airflow over the ailerons on deployment.

John