Z frame question - Yes, another one! :)

[Realnoisy]

So far I have sectioned my xmember 1.5, 2.5 dropped spindles and bags on my 65' LWB. I'm currently laying xmember but I have to go lower! I know I could purchase a PB dropped member but I choose not to go that route. I have read tons of Z framing threads but haven't located any threads that describe how to go about it. What I'm looking for is how to raise the frame rails after cutting the frame. Do you just put a floor jack under the xmember and jack it up? To me that is asking for trouble if it should move the slightest. I could be wrong, and that is the way to go, but I want to keep movement minimal. Or would one jack the entire truck up and lower the rear after the cut. Any and all suggestions are very much appreciated. Thank you!