Slider mounting question

Per the AFCO slider instructions, the slider bolt is supposed to sit a 1/2" behind the center of the slot. How you'll figure out that spot without the weight of the car on the ground I have no idea. When I did mine I slotted the brackets I made and mocked it all up to figure out the final location before completing the mount.

I mounted mine with a bracket I made to replace the shackle brackets. But I only have the 1/2" spring offset

img_2580_zpsuuetr2gp-jpg.jpg
Here's the AFCO instructions

slider_tech-gif.gif

@younggun2.0 used sliders as part of his spring relocation, he also notched the frame rails. You can see the pictures of his work here
Post your wheel and tire combos.