Has anyone used these Tire Guards from Gempler's. I have had to fix 5 flat tires while brush cutting this spring; All of them caused by thorns puncturing the innertube. I even fill the tubes with tire sealer and still get flats since the thorns penetrate about 1/2″ inside the tire and eventually rip a hole in the inner tube that the sealer can't plug. They are about $80 each for my 7.5×16 fronts, just want to make sure they work before I spend. If they work, it would definately be money well spent as far as I'm concerned. Thanks,