Not sure where I saw this (may have been the same video) but a while ago made 2 identical wooden spacers from some scrap 2x4 blocks with a piece of leather glued to the end and a hole drilled through. Just about 3/4" square and 2" long, and can double them up if I need to in a row. Just gotten in the habit of stringing 2 piece and if I use the spacer with the leather side on the frame on the outside and then the starting clamp behind the block on the start of the crosses. Even if the string is crushed by the starting clamp, that part will get clipped off when I come back and tie it off. On the mains I'm just careful to make sure if there is any crushing it stays on the inside of bed, and not looped around any holes. Doesn't matter if it's poly or natural gut, it should be good to go. Don't string a lot these days - just me, the kids, and a junior down the street from us, but I can't remember the last time I ever saw a string break at or around the point of the ghosting / crushing.