I can't remember the maths off the top of my head (I'm on my lunch break so haven't got time to work it out now) but I'm sure I did a bunch of calculations and posted on here some time ago (it could be 3-5 years ago, not been on here much the last year or two) stating the differences in pulley size.
If the supercharger pulley is smaller then it means that the supercharger is spinning faster than it would be with the larger, standard pulley. There is a point where the G40 physically cannot flow anymore air through it but I can't remember what speed the supercharger needs to be spinning at in order to meet that point. Anything over that point and the charger is producing no more boost. Pushing it further (ie making it spin even faster) will just result in breaking parts, leaking seals, bearings, etc.
Take a look with the search function from the main forum menu. I seem to remember something about 1.2 x crank speed, although no idea if that's to do with this or something else entirely. Also, try looking up Andy and yoof, they've done a lot of work on G40's and can be a great help!
If you do sit down and work it all out, post your findings on here as a reference!