If you're absolutely set on using mec wheels, but are worried about the wheels not holding up under the repeated stress of climbing, i definitely recommend making your own. in 2010 we made our own and the process was repetitive and a little bit tedious but fairly simple, and if you do them the same way we made ours, they'll be very sturdy. another bonus is that you can cast the rubber for the rollers in your own team color and have the hubs galvanized to look pretty also. if you want something to reference, you can look at my team's wheels on our website (
http://www.roboteknix.com/gallery/?&...71623918928449) or even look further in the past: in 2006, with the game Aim High, team 357 made their own mecanum wheels that they dubbed "Jester Wheels".
Just food for thought if you have a little time and patience on your hands.