Mike,
When I first installed my strobes (Same as yours, different vendor), I ran an independent ground to the firewall. This caused a good bit of noise in the headset upon strobe discharge.
To solve this problem here is what I did:
1. Ground the unit locally. In my case, I added a plate nut right next to the power supply.
2. Clip the aluminum shielding and braded shield wire at the strobe light. Continue the braded shield wire all the way to the power pack and ground it on the same screw you used to ground the power supply. I used knife connectors to connect this shielding at the wing root because I cut there. It would be best to run one continuous wires from the power pack out to the wing tip. (Just leave the wire coiled up on the floor until you get to the airport and run it out the fuselage and down the wings after you assemble the plane.)
After doing those two things, all is good.
The reason you don't ground the shielding at the wing tip, as I understand it, is that doing so will cause a loop and the shielding will work as a really good antenna to transmit the strobe discharge.
