Which ( brand of ) hingepins did you go with? There do seem to be two different versions for the maxx trucks on a few websites- apparently one version does have slightly longer pins for either the front or rear ( or both ) upper a-arms. You could always cheat though if you dont want to order more pins; drill a little hole in either the bulkhead or a-arm, then put a little setscrew / grubscrew in there which will hold the hingepin in place without the need for e-clips:
http://traxxas.com/forums/showthread...=1#post4404874
Great detailed pics from a fellow RC-M member.