You need four leaf packs since your taking the main leaf and in his case the second leaf out of each pack.
I think you misunderstood, you only need a donor front pair of springs and you're only adding one additional leaf to each of your existing 4 spring packs. You used the two longest leaves in each front spring pack for your additional four add-a-leaves. Adding one leaf per spring pack gives approx. 1.5" of lift without making the ride harsh.
The reason for only using two front spring packs is it offers the same amount of lift when added to all 4 corners, and the front packs have slightly more arch than the rears.
It's worth the trouble if your stock springs aren't bent or negative arched.
I went a step further when cutting the spring eyes off the top leaves by leaving about 1/8 of the spring eye. This slight upward curve supports the spring eye in the bastard pack and strengthens the spring where it needs it most, between the spring eye and the second leaf. This is where stock springs commonly bend.