The key is, there is no "correct" shackle angle. The proper shackle placement should allow the spring to have complete droop and compression, period. if when the spring is flat, the shackle is flat (or damn close to it) than your suspension is going to allow max compression and while the spring is stretched out, the shackle should be damn close to straight up and down, allowing maximum droop, which is whats wanted.
Regardless of the amount of gear, parts, whatever this only changes ride height. Does the shackle angle change? Of course. Point is, this doesn't matter. The shackle angle is only important in its relation to the spring position.
Regardless of the amount of gear, parts, whatever this only changes ride height. Does the shackle angle change? Of course. Point is, this doesn't matter. The shackle angle is only important in its relation to the spring position.
