That plastic is “carpet runner” and cost $.60 and I have a lifetime supply. It works perfectly, even with a couple legs missing.
Everything is homemade. I started using the tach to find sweet spots to increase speed for really long cuts with various bits in various materials. The Hitachi goes from 7k to 24k so had great variability. It took a WHILE to get the code right so it could measure 24k, but here is a step by step. It only ways a couple of ounces, but I used a full sized Arduino. You can use a microview arduino and it would be the size of a quarter.