RD04 additional chainslider

Old Africa twins usually have a bad driveshaft or driveshaft bearing. During full rear suspension motion, the chain tensions up quite a bit which usually causes said problems. But if you leave the Chain quite loose, it can scratch the swing arm (especially when offroading). This additional Slider, printed out of TPU, protects the swing arm so you can leave your chain loose, which should prevent those the mentioned failures.