Eddie,
I know what the cats are and aren't capable of doing, afterall I do hold a State of CA advanced smog license and there is no doubt that the State of CA has the toughest emission requirements in the country. We have a state run emissions program here in AZ as well and I have to say that it is the biggest joke in the world, I would have to say that 50% of the cars that pass here would not pass in CA. I don't know of any factory service manual that accurately explains the operation of the various cats on the vehicle. Another thing to take into consideration on stock vehicles with pre and main cats is that the factory has to build these and make sure that they will pass emissions for 8 years or 80,000 miles, to this day I do not know of any aftermarket setup that can guarantee that kind of performance. So while a person probably can yank the precats and get by with just the main cat in the short term it is not going to be able to maintain those levels in the long term.
ANother thing to think about on a pre and main cat setup..have you ever wondered why there isn't an O2 sensor behind the main cat for monitoring it. Simply put, what people consider the main cat is more for NOX control than anything and while it does clean a bit of HC and CO in the process it's main function is still NOX control. The pre cats are there to reduce HC and CO, without proper HC and CO reduction the NOX reduction can't take place.