You might want to consider building your aircraft with as few gaps that require filling as possible. Check your parts fit before gluing,and fit accordingly. Makes for a much stronger and rigid aircraft. Use the thin CA forframing. After framing and the initial building process is completed, go back over any joint you may be unsure of with the medium/gap filling CA.

If you get a gap you are unhappy with, and cannot fix in other ways, apply a small amount of baking soda over the gap, then add a drop of thin CA to the baking soda. This will fill the gaps, and strengthen the bond at the joint.

Silversurfer