I don't know why people are fixating on the "adhesives." All of the materials used in our planes shrink and swell in different proportions, direction, and at different rates throughout the lifetime of the model. Exposures to extremes of temperature and humidity cause changes regardless of how old the model is or how long the resin has cured. Resin definitely shrinks during the initial cure, but once cured (assuming it was mixed appropriately) should be one of the most stable materials in the structure. I would add that the best integrated composites benefit from thorough penetration of the entire adhesive matrix and cross directional substructures...locking the different materials together. This is extremely difficult to do in a "built up model" since at least one side of your wing skin is "unfinished" allowing moisture penetraion to the balsa which is an extremely porous wood with directional grain. Light plywood is more stable and a better choice.

At this point, as for a solution, I'm agreeing with the panel line guy but for different reasons; Not so much a visual distraction, but rather thinking a heavier paint surface (a byproduct of doing panel lines) using a flexible paint (like latex) will better mask the movement underneath. The type of paint used has not been discussed but a common problem is expecting automotive finishes (which are hardshell finishes formulated for metal and hard plastics) to withstand the unstable substructure construction as well as the flight stresses and airborn flexing of a model airframe. Latex paints are used on houses because of their ability to flex with the materials beneath.

My last two cents on the subject