I have to hand it to you...your skid tray knowledge is impressive.The skid tray which requires the two metal brackets is GRP...actually reinforced with aramid/Kevlar fibres ...& totally wrecked several new jigsaw blades when I had to alter mine to fit the Tiguan subframe cover.
There is also a thin plastic aero tray which is the same size & is in GTE spec (loads of vents), Diesel noise insulation spec (one or two vents)..& eco spec...no vents...
There is also the Mk8 Golf eco huge tray which is the same thin material, but also fully covers the front subframe..right up to the start of the exhaust tunnel...but really requires the Audi Aluminium subframe due to the rear fittings..