Made mine on Friday night, ready for Sat AM ride:
Pair of old 2.1 Panaracer Trailblasters, 200x15mm + 75x12mm screws, and way too much spare time
I lined them with about four layers of gaffer tape, but after about four hours of riding, one pinch-flatted. On inspection, almost every central screw-head had 'burst' through the tape and marked/pinched the tube to some extent. One obviously pinched it all the way through. Reckon some additional DPM, an old (extra) inner tube, or a strip of non-descript, tough, flexible plastic would make them perfect.
They were alarmingly effective, and dealt especially well with compacted snow on steep tarmac climbs. Also good at picking up leaf-litter



