It's been discussed here...
http://oople.com/forums/showthread.php?t=61752
Seems there are two ways to get on those rims. First is to stick to Tamiya hexes but use a thin washer as a spacer (between hex and rim). 2nd is to drill out the B44 hex, then bend the B44 pin into a slight curve and get it into the holes (the holes are perfectly aligned, so you need the curve).