Precision is how closely the ball will follow your intended line, Forgiveness is how much the putter will try to move a mishit putt back on the intended line,
Precision no matter how high it is does no good if you miss the ding by very much, Forgiveness only comes into play on putts that you missed the ding. Forgiveness won't make up for a putt that the ding was missed by a lot.
Neither forgiveness or precision will make up for a poorly lined up putt.
To make the Spider or any other putter for that matter work better you need to read the greens well.