I have always used Monokote until I bought a couple of H9 ARF's and did some mods that required the use of Ultracote. I have noticed the Ultracote shrinks a lot better than Monokote but after a trip to the field, wrinkles re-appear whereas my Monokote covered planes stay tight. I'm stickin' to Monokote wherever possible.

Cheers,
Andy