Why won't the ones I listed work? They look like the same style as these, which are recommended by HPI for use with those wheels:
http://www2.towerhobbies.com/cgi-bin...?&I=LXKSC1&P=V
I realize the axle diameter is different between the two, but it appears that the flange on the hex adapter fits through the inside of the wheel hub on either set of adapters.