I ride a fair amount on Rails-To-Trails surfaces which are gravel based. Had a flat in May 2018 and when doing the fix on the trail, I also put a piece of duct tape over the small puncture on the inside of the tire. Just had a flat last week on the same tire(piece of glass this time) and noticed that a fair amount of grit had infiltrated through the May 2018 puncture and lodged as a bubble under the duct tape. With no duct tape, all this grit would have been inside the tire and rubbing on the tube. I was not able to find any tire repair instructions that discusses this possible grit infiltration. So, from now on I think I will continue to use a small duct tape patch on the inside to catch the grit. Any thoughts on this?