Speedo: I've ordered the hollow top shaft from Speedtech R/C. I expect to have it tomorrow.
Our season is just about to get started, so it may be a week or so before I can give any feed back.
pilot: Last season when I ran my Special, I experienced the same wheel jitter that you describe. As it turns out, the standard blue aluminum universals wear very easily! The slop that develops then contributes to that problem. The universals are rebuildable, however, I think that in the long run purchasing a set of hardend units would be cheaper.
maski: I don' t think that you can use the Yokomo InchUp wheels with any of the MR-4 series of cars. If I remember correctly, there is a problem with rubbing because the offset is different. It's really to bad, since the InchUp wheels are really nice looking and in expensive. I used to run them on my YR4-M2.