Those supports were on my shee when I bought her,they work awsome plus you can change your rear fenders angle.It helps them stand up instead of lookin droopy,and they keep the fenders from vibrating when the engines running.
I used the rubber boots and fender washers,when you tighten the washer down the rubber boot will scwash out and exspand and hold it good.The rubber will also help with the vibration.
Well dont get me wrong A 4mm crank makes awsome power and can be run on the trails,but it costs A good amount more than just bying the kit.You get A good builder to do your port work and true and weld your stock crank for strength you will get some great power gains.