I use Flapperon mixing to Elevator for some 3D stuff. You need to have the flapperons go opposite of the direction that the elevator is going.

Example: In a Harrier the elevator is going to be up, trying to hold the nose up. You want the Flapperons to go down at this point. That will also help hold the nose up. It does help to tighten loops because the Flapperons are helping to pull the nose around.
There was some talk about which way to have the Flapperons go a few days back on here and I think the consensus was to have them go the same direction as the elevator for a Harrier. I dont think that is correct. You will have the flaps and elevator fighting themselves. I tried it the other day and it just doesnt work.

As for hovering. I usually turn the ELEV/FPPR mix off to soften out the pitch movements.