I know this might be a bit late, but I only recently found out that this Mario Kart Wiitournament was still running and ends on June 24. For the unitiated, you have toknocka triple succession of two Spiked Topmen out of the arena only receiving Triple Mushroom items to aid you. After every 30 seconds or so, another of the three outer rings of the colosseum falls away.
So far, playing through the Spiked Topman challenge is quite exhilarating. It reminds me of Time Trials in the sense of requiring pattern memorization skills combined with quick reflexes to get the best time, not to mention the endless string of failures before a success, yet it's refreshing to seea new strategy to masterand pull out a vehicle I would not have otherwise used in a regular race. I would start off with a plan of attack after figuring out the Topmen's movement pattern, then discover as I repeatedly put it into action a better way of doing things and thus adapt it to my overall strategy. Yes, I could simply study the YouTube videos of it, but I find it more fun to figure things out yourself. I'm not in it to win since I'm nowhere near as skilled as even many GameFAQs denizens, but to do my best and see how far I can go. I'm currently at the 49 second range, which is pretty lousy if you compare it to the 18.8 seconds (give or take) of the world record, but it's still an A rank apparently so it's satisfaction enough.
It's a pity though that this is a limited time event. I'm suspecting that Nintendo prefers to attempt to even out the amount of practice time the competitors have, but it's still disappointing that suchchallenges can only be experienced once a year and that if you hear about it too late you've missed out indefinitely or even forever. I would love to leisurely try this on my own time tohone my skillsrather than stress about time limits, so it's too bad things like this have to be reserved for special events rather than be included in the game itself. Oh well. I anticipate seeing what they have next year.
UPDATE: In the end, I got 23.832 seconds. Not a bad time, I think. The world record is currently a little above 18.6 seconds.