The manuverability will go up nicely!
Rolls should be faster, loops smaller in diameter..
But the glide will suffer.
On my SIG Ultimate which has two thick wings, the plane must be on final close to landing when the engine quits.. it comes down like an anvil poeer off.
Low speed will need down elevator to keep the speed up when landing.
I think bipes have been done with Stiks... I've never seen one, but it does use that spare wing.