I've been promoting these things for a long time. As far as I'm concerned, unless you have an old beat up 1948 Dodge Power Wagon with 1.6 tons of extra steel plating added, Hi-Lift jacks are just bad news. They make great can openers on your bodywork when they slip. (Notice I didn't say "if" )

They don't need a lot of pressure because they're a large volume air bag. PSI means pressure per square INCH. So the area on the almost 28" diameter bag end which is about 615 inches, even at a measly 1 PSI, that's 600+ lbs. of lifting force. Only 5 PSI is over 3,000 lbs. That's why the exhaust works. Your compressor will work okay, it'll just take a while.

Another reason I think an X-Jack is required trail equipment, is in case of a rollover where someone is trapped. They're thin enough to cram in somewhere to get the rig off someone.