The front lifts 150% of the spacers actual size. So if you have a 1" spacer, the lift will be 1.5".
1" spacer = 1.5" lift
1.5" spacer = 2.25" lift
2" spacer = 3" lift
You can safely use up to a 1.5" spacer in the front without any major problems. Your joints should be okay, but if you have old CV shafts, you could get a torn boot after some time. Also, the lift is only limited to how much down travel you add to the strut. You should add the same as what you lift it, or more, but no more than 2" without lowering the front axle.