If you don't shoot that bow much, the arrows impacting left might just be a function of your brain not adjusting the hold correctly. If you shoot instinctively, not lining up the arrow on the target, holding the bow as you would a bow cut more to center actually points the arrow to the left, and that's where it will go.
On the other hand, if you do have the arrow in your line of sight, your brain should be lining it up on the target, and a left impact would indicate a too stiff spine, unless, of course, it's a false stiff caused by a too soft spine glancing off the bow side plate. A brace height that's too low can cause the same thing. I suggest raising the brace height and adding about 10# of spine weight, which should put you right about at the bow weight at your draw length.
Keep in mind, too, that a very light bow and arrow is very sensitive to any errors in form. Good luck.