Your question made no sense to me. I am glad Joe H. figured it out. I was trying to think, Half or 3/4 of what? Inches, Furlongs, Dichfors.... The 1/3 rule Joe mentioned is good, and works well with standard automotive fair. In the heavy truck industry, almost all suspensions are set with nearly equal amounts of jounce and rebound. So the shocks would ride at the mid point of their travel at ride height. Of course, most heavy trucks are air ride with the ride height controlled with either height control valves or electronic control valves. The off road guys prefer to go with even more ride in, often 60% rebound or more. This keeps the tires in contact with the ground over rough terrain at high speed. Trophy truck suspensions are on the extreme end of the spectrum. All depends on what your building.
Keep in mind when measuring that on a new build the car will settle about an inch or more in the first few hundred miles of driving.
A good explanation of what you're wanting help with always helps to get your question answered. We can't read your mind or see what you're working on if you don't post pics.
How dare you try to understand a poorly stated question before offering advice that was solicited. That'll teach ya. Sent from my LM-V405 using The H.A.M.B. mobile app
Grammatically speaking, your question asks how far out do you pull the mounts. So, since we mostly speak English here, it's easy to understand why few can understand your question. Maybe try this: "I am building new mounts for my shocks. I need to know how far the shock should be extended, so I can get the correct length of the mount. Thank you in advance for your input." At over 700 posts, you should probably have a handle on how this place operates by now.