Hey Tiger, glad to see you at it! Building is the best part of this hobby but that's a secret so don't let it out. Even my ARF of the SSE has some gap at the trailing edge so I would say your plane would perform fine as is BUUTT... You have the oportunity to correct it. I would trace the root rib and make 2 coppies one for each wing and epoxy them to the existing root ribs and block sand flat, attempting to get the same length out of each wing half. But if anyone comes out to measure the 1/100th inch difference you may have... kick them in the shin

I am sure there are other ways to do it so wait untill you get some other sudjestions before doing anything perminent.