I used to cut my own tires all the time when I was racing sportbikes. We had to use DOT tires for the class I was racing. I would cut more grooves in them for the rain races and it was night and day better than the stock version. Cheating? maybe....

The tires started as DOT's but there wasn't anything in the rule book against cutting my own treads.

Cutting more treads is extremely easy and you can make some awesome looking tires. Show up at a ride with some cut tires of your own and all of the guys will be asking where you got them.