I've had this problem on a few of my planes - the worst offender was the upper side of the gull wing on my F4u Corsairs. I tend to agree that something's up with your installation - definitely need to use separate koverall pieces for the stab / fin, and perhaps you need to give the dope / stix-it more time after installing to dry and setup before you heat shrink?

Regardless, pulling does happen and may be caused by something on the wood, something on the fabric, something on the something, etc. Could also be that you're heat shrinking too much and the dope is proverbial straw that breaks the camel's back.

My long-term solution was to switch to Randolph's non-tautening dope and to get the tautness I need by heat shrinking.

EG