This morning I sealed the longerons and perimeter edges with watered down PVA. Then this evening I cut a paper template for the top deck covering. I used an off cut of turquoise Oracover to shrink down and leave the very distinctive ribbed shape.
I then masked around the Oracover leaving a small 5-8mm margin for the fibre glass to adhere directly to the surrounding balsa. Then I sprayed the Oracover with a list mist of 3M spray mount and then carefully applied the 200g/m2 of woven fibre glass. Using the spray mount securely holds the FG in place whilst wetting out and has no adverse effects. Using spray mount also allows you to really work the resin in sparingly without any puckering up or excessive movement or floating FG. I swear by the stuff.
All wetted out and overall I'm very pleased with the result. Hopefully, this method of covering will prove robust enough for some slope abuse.