I have a low wing "Stick" type airplane and an extra wing. I would like to experiment with convering the plane to a bi-plane. ( what else would you do with a spare wing??) Anyway, the questions I have are: Wing spacing amount? Wing Staggering amount? CG??

ANY advice would be appreciated.
Thanks in advance.

The drag of two Stik wings is enormous!
If there's no stagger, the c.g. won't change.
If you have stagger, put the c.g. at the 30% point of the chord you can see in the top view.
At least 80% gap between the wings.

Would the drag be too much? What would suffer besides airspeed?

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.