On my Lochstar I have the elevator working like a Northstar, plus I have the ailerons set up as elevons, plus I have the foreplanes all moving, pivoted about 22% mean chord and moving about +/- 6 degrees for pitch control, and about +45 degrees for airbrake. That gives a nose up pitch which needs some down mixed in on the other controls. They may not be necessary but certainly give a steeper descent angle.
Pitch control is very positive and the model will loop and bunt quite tightly. I can't say exactly how much of that is due to the foreplanes. They probably do not contribute a vast amount as their area is only about 5% of gross wing area. My last 2 Northstars had elevons as well as elevators and were also quite lively in pitch.
The main reason for trying to use foreplanes as airbrakes was to asses their usefulness in a jet seaplane I am designing.