Simple I always like simple. I must concur with my buddy Chris is Me. Look into the Andy Mark Nano Tubes just a suggestion but not necessary to build a very functioning mecanum drive system. My FIRST team (272) minus 2009 because they would have been illegal has used mecanum since 2007 and we are in love with them. Software and a Rigid Squared Structure are the keys to success here. If the wheels begin to candum your control, especially in a crab (side to side) motion becomes sluggish, innacurate or drifts in an undesired direction.
If you need help with the code please email me and I can show you what we have been using for years. We code in C++ by the way.
irishpridel@hotmail.com