Will a radiant barrier work under fiberglass insulation?

Hi, I have a south Florida climate. My house has light colored shingles, Raft-R-Mate below the plywood for air flow and ventilation, then r19 fiberglass insulation between the rafters.

If I put a radiant barrier below the insulation, stapled to the bottom of the rafters, would that do anything to keep my atic cooler? I know everyone says you need an air gap to be effective, but I can't really find any information about putting it below fiberglass insulation.