My take on it having done many, attended training courses at the AEA and talking to industry experts.
Throw away all gaskets. After installation seal around perimeter with either Pro Seal (best PITA) or Permatex Right Stuff gasket maker (Autozone, etc...)
More specifically:
Again. Throw away the gaskets. Remove the paint from under the antenna footprint (outside of skin). Remove primer from inside of skin in doubler footprint if the skins are primed. Clean and alodine both inside and out. Rivet doubler to skin making sure rivet holes edges are bare metal. If antenna doubler is primed or painted on non-contact surface run a piloted burnishing brush with a cordless drill on the interior surface of the doubler to remove any paint where the attachment washers and nuts make contact as applicable. Install antenna being mindful not to over-torque the hardware (see specific manufacturer instructions). Mask around base of antenna with fine line tape both above and below the base. Apply a bead of Pro Seal (yuk) or Permatex Right Stuff (yay) gasket maker around the perimeter of the antenna base keeping material within the fine line tape. Use finger wet with soapy water to trowel a smooth radius of the stuff into the interface. Pull fine line tape while the sealant is still fresh and touch up. Any excess sealeant can be wiped off with a soft rag, applying soapy water as necessary.
P.S. Ditch the gaskets. If you feel you really need one, then buy one of the aftermarket gaskets compoosed of gell substrate with wire mesh imbedded in it. The mesh provides electrical bonding to the skin. Beware. They are pricey. I have purchased such from Av-Dec H-Tak gaskets in Fort Worth, TX. They aren't used to selling to GA as they typically supply military contracts, but they can cut them to match for most any commercially available antenna. In the final analysis it's really not worth going this route.
https://www.youtube.com/watch?time_continue=94&v=0Kf4aG4OLmo
If you worry about corrosion on and exposed prepared surfaces or hardware coat these with Pro Seal or Right Stuff.
Summary:
Ditch the gasket
Prepare the interior and exterior skins for direct contact with the antenna base and doubler.
Protect bare surfaces with alodine.
Seal final assembly around the exterior antenna perimeter with Right Stuff or Pro Seal.
Live happily ever after never having to worry about electrical bonding, ground plane, poor radio reception, or metal corrosion. Also cures the heartbreak of Psoriasis, the embarrassment of halitosis and the indignation of the guys at muscle beach kicking sand in your face.
I think.
Jim