Need advice on this shackle angle (Pics embedded)

[Stephen]

measure your angle when the spring is it's longest, like when a 52" spring is, well, 52" long. 20-25 degrees is the max range. 30 is too much. If you try to compress the spring past flat with too much angle it will get so stiff it essentially locks out. 56" springs are often stiffer to start with and they don't need any extra stiffness from shackle effects.
shackle flip backward with 56" springs and 7.25" shackle is a 32 degree shackle angle. With a shorter shackle it gets worse. You need to move the flip back farther.

 

[handloader90]

Thanks for the info! Is there a good way to find out exactly how far I need to move the flip back on the frame without drilling multiple sets of holes? Maybe C-Clamp the bottom portion of the flip to the bottom of the frame rail and mock it up from there? Don't think the C-Clamp(s) would hold everything together with the weight of the truck sitting on them.