does a severe helical stabilize an arrow raster and make it more forgiving?
Yes. Size of the fletch also has an effect. The larger, the more stabilizing.
That said, more is not better it only masks the reason the arrow does not stabilize faster. If everything else is correct then minimum fletching is all that is required in stabilizing the arrow quickly. Altho spine is important its not the most important factor, the nock being on the shaft straight is the most important aspect of building a proper arrow and the most over looked.
Bob