Thanks to Jeff for submitting this modification to eliminate tail wag :

Myself & my mate both have TRex's and have struggled to get rid of the tail wag, despite putting 401 gyros on & crashed as a result. The problem is that the blade holders won't rotate freely on the shaft. What we've done is dremeled out the plastic just slightly, this has given us a beautiful freed up tail & eliminated the tail wag on both Trex's.

I've coloured the hole red that we have dremelled.