That looks to me like you would get 5psi all the time and 9/10 when you flick it.
If you want normal 5-7 with the option of 9/10 with a switch, leave one of them unswitched, piggyback off the power for the other one, put a switch on the earth of the second one.
so you will have normal 5-7 if the switch is not flicked, but if flicked, you will have 7 which will go up to 9/10 at 4500rpm.