OOps! I missed the fact that this was a pre-covered ARF. In that case the fiberglass reinforcement can't be done unless you peel back the covering. I think you were OK the way you were without the fiberglass. Putting the reinforcement outside the covering won't do as much good. It has to bond well to the wood surface. Non ARF kits and cover-it-yourself kits come with the strip of fiberglass cloth for the reinforcement. Some people use CA to attach it. I prefer the epoxy as described above.

I hope you get the plane back in the air. What you have added to the wing shouldn't hurt anything.