I don't know if this would work on a flip over, but I have waterproofed tents by using mineral spirits and 100% silicone. I think it's about 5 parts mineral spirits to one part silicone (could be wrong on that). Just mix it super well with a drill then paint it on with a foam brush. The mineral spirits will evaporate and leave the silicone in the fabric. There are a lot of videos on youtube about it.