I have tried most diy tens and the spoon tens works the best for me. (Good flex and spring). I made one from a old file but it makes the bb feel like it has sand on the inside, I like the one where you use a crank chainring and just wedge it in between the chain. (Upper chain moving back and lower chain moving to the front with chainring in between) Only possible if your chainstay is made in a way that there is clearance for wedging chainring. It looks awesome having 3 gears on a singlespeed.