If you don't want to show any fixings on your front cycle wings and you don't want to risk vibration cracks in the GRP then bond them to the supports. This is what D.J.Sportscars do on the Dax Rush, the adhesive they use is the stuff windscreens are bonded into place with and they say the bond is stronger than the glass fibre itself. The same technique can be applied to clam shell wing stays.