I've scratch built a 150% version of the original Electrostreak that was popular in the late 1990's. (Still got two of those originals)
This model was built in 2003, and has well over 1000 flights on it. It's been flown only once this year. (Most of my flights this year have been on my new Hacker A60-16M powered giant scale Extra 330, running 3000 watts.)
Well, took the Electrostreak out of my pickup today, and took a look at it's tail feathers. The super monokote had several very narrow three inch long slits or tears in it, both in the vertical stab, and in the elevator. (I replaced the covering on the wing in 2010 for this same reason.)
The old monokote in this model has the tear resistance of a piece of cheap cellophane wrapper on a bag of chips. To give an idea of how bad of shape this top covering was, dropping a standard penny from a height of two inches went right through the monokote. The monokote on the underside of the elevator survived a penny drop from three feet and is still in good shape.
I'll be stripping and recovering all of the monokote on the tail feathers of this model before flying it again.
Take a look at the attached photos:
Bottom line, if you've got models using those shrink type coverings that have seen a lot of sunlight, take a critical look at it's covering.