Installing and Preloading Ballscrew???

[iaknown]

Hello all, I recently purchased a Mighty CNC vertical mill, similiar to say a Fadal 3020. I had to almost completely disassemble the entire machine to get it down the hall and out of the building is was in. This included pulling out the Z-axis ballscrew to gain some height. I reinstalled it today but held off on tightening the end nuts because I wanted to get some input. There are the carrier bearings and then outside of them is where you tighten the nuts to preload the ballscrew. How much should one end be preloaded against the other? Or how much should the ballscrew be stretched, if any? Any rule of thumb because there is nothing in the manual about it and support for this machine sucks. Thanks in advance guys.