hi bob, i did this a few years ago , there are some pics in my album. i originally had to early 6 gal tanks. i installed 13 gal tanks which required removing a rib and relocating the drag tubes. i did one wing tank one winter and the other wing the next winter . the two 6 gal tanks just wasn't enough gas for the way i fly.
i didn't remove all the fabric , just what i needed to do the job . although the wings had been covered in the 90s the plane had never been flown or completed and never in the weather .
before you ever start to cut the fabric off be sure to clean the new tanks as recommended and leak check the tanks . i did have a tank that leaked and i had to return it for repair or replacement . great people to deal with at kitfox.
feel free to ask if questions come up