Sounds like this one is gonna be stalled at any speed!
My guess is it will handle like a brick with the flaps down and engine out. Would some aerodynamicist like to put the appropriate model parameters into the computer and tell us how bad this thing really is?
Assume the flat boards are hollow rather than solid and the thing is fitted with some powerplant capable of delivering enough thrust through a fixed-pitch airscrew of Wright-Flyer efficiency to actually get it moving.
Gonna handle like a dog, all the same. Its bite will definitely be worse than its bark!