I assume you are still building and not finished the kit yet. First thing to do is get all the incidences correct. Check both wings and the tail group. Then mount both wings. AFTER the bottom wing is mounted and you are satisfied with the incidence go back and fill the gaps with micro balloons and epoxy. It is not hard to do and will make a perfect seal.

1. Iron on two strips of monokote on the bottom wing where it contacts the saddle. It must be about 1" wider on each side of the fuselage.

2. Mix up a batch of micro balloons/epoxy and dab it on the wing saddle all the way from front to back and on each side.

3. Bolt the wing to the fuse and tighten.

4. Clean off the excess that oozes out with a putty knife then let dry.

5. Once cured take out the wing bolts and tap on the wing until it pops off. It won't be all that easy. Be patient, it will pop off after you tap for a little while.

6. Remove the monokote and sand the fuse sides smooth.

The joint should now be perfect. I always do this prior to covering.