Aircraft antennas

Hi, I am about ready to cover my Cub type airframe, but need a place to
attach a com antenna. I was considering brazing a plate to the airframe so
that it would be just under the fabric. The antenna is the type that has a
ceramic insulator on the bottom of the antenna that insulates the stainless
steel antenna from the airframe. Does the antenna need a large plate for a
ground plane or will a small plate be sufficient? If a ground plane is
required, can the copper foil tape be used on the inside of the fabric as
the ground plane?

Charlie