Food for thought. Most of the ARF wings are not glassed in the center, but just epoxied together with a strong joiner. I've tried this approach on a couple scratch built wings as well as on two ARF wings. I have also built two 4*60 where I used the CA on glass tape. All of these have crashed beyond repair, but none of them broke up at the center section of the wing. No difference in strength that I could see.

Now, if I'm kit or scratch building, I span the center with the bottom sheeting. Easy to finish and easy to sand. Just as strong.

Don