What is the benefit of taking the cats off anyway??
With todays performance cats you won't see hardly any decrease in performance by running them, and if you keep the same size stock exhaust and just take out the cats I bet you would pick up next to nothing in performance. A new air filter or some timing advance would probably would give you better gains and no hassles.
Hydrocarbons stink, and if you let more flow out the pipe... its gonna stink.