You said you shoot lefthanded and your arrow was impacting to the right. The general wisdom would be that this indicates too weak (for a LH shooter), rather than too stiff. So you decreased the point weight (stiffening the arrow), and it moved your POI to the left, as one would expect. I don’t think this is an example of the reverse effect that I wrote about, but it is does show that we have to keep an open mind when we are tuning with fletched shafts. From what you have stated, I believe your .800 spine predators should work out well for you. good luck!