Why do you want the elevators to act as flaps? I've never heard of that before so you have me curious as to why you would want elevators as flaps?
Just me thinking, but if you had your elevators already down, then you are actually losing some authority of the bird in take off and landing, as having the elevators at the rear of the plane, the minute you're trying to drop the elevators a bit, your bird is going to want to climb, which will have the effect of slowing it down, but i'm not sure it's going to create the characteristics you want.