Re: rear sprockey alignment
I have used the "wedge" method with pretty good success to help reduce the up and down "wobble" on a sprocket....
Basically, look to see how much space you have between the sprocket center hole and wheel hub when the sprocket is perfectly centered...
Now find something small enough to use that will fit that gap (I have used cut paper clips with great success and the good thing is they come in different sizes).
Cut several pieces and Wedge the cut pieces in between the sprocket opening and the hub of the wheel (minimum of 4 places, 5 or 6 would be better).
Now tighten the bolts in criss cross fashion tightening the bolts a little at a time....The wedges will help keep the sprocket centered.
I was going to remove my wedges but they were in so tight I couldn't pull them out with my needle nose pliers so they are still in to this date! (I did use end nippers to cut them more or less flush with the sprocket just for looks).
With the rubber factory mounting system it is nearly impossible (we OK impossible? ) to achieve a perfect wobble free mount....YOu can get fairly close tho with time and patience
The only way to achieve a wobble free sprocket mount is to directly mount the sprocket to a disc brake hub or by uising the Top Hat Sprocket Adapter.
Hope this helps you.