Polyairs give 4" lift

I looked at Coil Rites, OEM Landrover bellows, and Poyairs. Based on convenience and cost I went with the Polyairs- $490 fitted.
With 5 PSI they give no lift, but with 25 PSI there is about a 4" lift on the unladen vehicle. With about 15 PSI there is a 2" lift and the suspension feels firmer. I have yet to load up the vehicle with the Polyairs installed, but you can see from the photo attached to this that the car was way down with the heavy trailer attached to it. Mind you, the trailer is carrying 21 jerries of fuel, two by 25 L of water, plus other gear, so there is a fair downward force on the Treg hitch.