Yes, trust me I know about SC's and what's needed to make them work properly, at one time I was going to SC the 7m. It's not so much a set pulley size as the speed relation to the crank speed, underdriven where the crank is turning faster than the SC, overdriven is just the opposite, it's very simple. There are many calculations and airflow charts for determining what drive % you should run for a certain engine, blower, and so on. You can use a gilmer / 8mm / 1/2" pitch belt on a centrifugal with no problem if you figure the right number of teeth to get the blower speed right. People ruin their engines that way the same as they do with turbo's, because of bad tuning or no tuning at all from just tacking on boost. As for twins, they will not spool faster than one equal sized larger turbocharger because of the simple fact your cutting the engine in half. Each smaller turbocharger is only fed by 1.5L, the only way they will build boost faster than a larger single is if all the engine's airflow is diverted to one of the two twins, a sequential setup, or diverted through another turbo like derby already said. Much to complicated and expensive to setup IMO because of the simple fact "lag" is overrated by owners who don't even have or haven't even driven a turbocharged car. If you size the turbine and all other related parts correctly to the engine you will have very little lag, unlike a T88 on a B16 that a ricer installs for the sound. Anyway the saying in the racing world is "build for HP, gear for torque" since torque is multiplied through gearing, lower gearing will make more power at the expense of speed. Of coarse it should come out the same since torque and HP are derrived from each other. There's more than one way to skin a cat.
