For Pikes the spacer goes above the top out bumper washer on the air shaft. If you add a 10mm spacer you reduce travel by 10mm. So if you have three 10mm spacers you will reduce travel by 30mm. That will convert your 140mm Pike to 110mm travel. I don't know whether it's recommended to fit more spacers, but what length of travel are you hoping to achieve?
As I said above, if you add more air to the negative air chamber than is in the positive, the fork will suck down up to 10 mm more, but the spring rate will stiffen, meaning the fork will need more input to react to bumps (reducing high speed compression) but make the fork feel bottomless.
Try fitting two spacers and then pumping the positive to 130 and then the negative to 140. That should give you 115mm or so.