The feathers should not matter.
As for the rest, I can only guess, but as it is flat with no cut in, you probably want a spine a little under the draw weight. But, for the a perfect shot there are so many factors to consider. Just to name a few, the bow width, the arrow lengh, your skill, your draw, etc.
I have no expertise, but I would get a variety of spines between 40 and 60 lbs and see what works best.