There are two adjustments you can make to get this result.
One way is to shift the base PSL of the SW down 5 points (I'm assuming you're using LWAMI values, BTW); from 55 to 50.
Another way is the flatten the rate of PSL increase with speed from +18 to +10. (the "c" value on the thust page)
Or, you can use any combination of the two in between.
Munchkin. :p