Hi,
"IF" your wing has a completely sheeted surface (like a foam core wing) and "IF" you completely attached/sealed the Monocote around the edges before shrinking, especially if you used a heatgun for shrinking, you may have trapped air between the Monocote and surface of the wing. If this is true, you may be able to pin ***** the Monocote near one edge, slightly heat the Monocote and carefully work the entrapped air out through the pin *****(s).

The process of "working the air out" is accomplished by carefully pressing the heated covering down to the surface of the wing while gently pushing the air bubble(s) towards the pin *****(s).
The *****s must be open all the way through the covering to allow the air to escape but will disappear as the covering is adhered to the wing surface.

When using any of the plastic films, I think it is a good idea to leave a short length of one of the edges unsealed to allow air to escape while shrinking/attaching the film to the surface in question. After shrinking/attaching, the remaining edge can be sealed.

Hope this helps,