Putting a patch on the sand through will leave you a high spot. You'll be better off to fill the low spot. Are you going to fill the weave or leave it to show through the finish coat. Fokker what? WWI plane or otherwise? If you plan to fill the weave then I'd suggest you fill the sand through at the same time you apply the finishing resin but add some filler to the finishing resin to help build the low spot. Talc does a good job and won't make the area to stiff to sand.