I've never had a sidewinder and I wonder how much movement side to side should their be in the rear axel? I have some movement so I wondered. I looked on the site but didn't find anything.
And if you want to do a really nifty job of optimizing the rear track, whilst reducing friction, consider the SIPA47 & SIPA52 spacers made for this purpose, finishing the job with a drop of lube at each end.