One thing to look out for is to make sure the dihedral brace (joiner) is
a snug fit and that you are getting a flush fit of the two root ribs. I've heard
some of the joiners on some ARFs fit pretty sloppy. A little sanding should
get both wing ribs flat to each other.
I treat ARFs just like the ones I'm building from scratch. If it doesn't look
strong enough reinforce it. Just don't get carried away and make it too heavy.
They're designed to fly, not crash.

tommy s