What most of us in citrus county use is a long whip c.b. stainless antenna. You know ,the redneck pickup style. Then cut off about 12 to18 inches of the top. Reason is when it whips around from a turn or a 360 ,if you leave it long it WILL smack you in the head! WHUMP UP SIDE THE HEAD! Your not done yet, you now weld (stainless) 2or 4 small stainless washers at the appropriate distances (as per the grommet holes) for the flags. Then the flags can be mounted with nylon zipties. If you dont have a mounting bracket already on your rigging, you can use a c.b. mirror mount like on big trucks, best placed back above rudders.
The problem with fiberglass is they break when they smack things like trees and other stuff.