Leave it to Riff to integrate an advertisement into his answer.

I'll caveat here that I haven't bought bigger tires (yet), but from everything I've read you would need significant cladding trimming to make it work. Dig around in the galleries or in Rickshaw's tire and rim thread, as I'm sure there are some folks running massive tires. Based on the pics I've seen, you'd probably need to cut away at least an inch or two from the front cladding. That's not a small, barely noticeable triangle on the inside of the cladding like some of the 285 folks have - it's more like cutting a significant portion of the cladding off all the way around the front (to make it looks decent IMO).

Agree with Riff and VXorado (on the loss of power issue) - doesn't seem like a good investment.