My Extreme mechanics for my EC-135 did not have a grounding strap. Maybe that was added to a later revision of the mechanics. That said, I never had any problem with static build up, or more importantly, any glitching due to static build up.
The MAXI-JOKER uses a grounding strap, and it really is necessary there. It has a belt going from front to rear, and the carbon fiber tail boom is isolated electrically from the main frames. So a piece of wire is used to connect the boom to the mechanics frames, so continuity is ensured.
Sooo.. there's really no equivalent problem with the Extreme mechanics though. Yes it uses belts, but, nothing that goes back to the tail boom.
Of course, if you want to ground the tail boom to the frames, no harm done. I'm just not sure that's really going to change anything for you.
I think I'd "try" the grounding strap, then if that doesn't work, be prepared to look for frayed wires. Also, make sure your receiver is not too close to your HC3x, and also is not too close to your ESC. All three devices emit noise, and as much as I'd like to believe the 2.4GHz radio is not affected by these sources, well, they are. The RF front ends can be overloaded by the noise from other devices when they are too close. Glitches can happen from this, and it has happened to me when my SK-360 was too close to my XPS receiver.
What's too close mean? Right next to each other is bad. Isolate them by 3-4 inches at least.
I hope you figure it out. And if it's just a grounding strap, well, at least it was an easy fix!