ORIGINAL: lukesp
Cent,
if they are the last of the Cox offerings, i.e. from surestarts with the cast crankcase then you will find the crank is a sloppy fit in the bush. According to Dan Sitter these crankcases are Chinese made, the earlier Dragonfly cast crankcases were a better fit although I can't remember where he said they were made. Dan sells or sold the original c/cases on ebay as coxmania. So if you bought em from coxmania they should be good.
Luke.
In regards to the sloppy fit of these DC crank cases, I believe this will allow higher RPM with a balanced prop. LM Cox did this with the Killer Bee crank cases. They called this a "relieved" crank case for higher RPM. It is designed to have less parasitic drag on the crank shaft.