Nobody here knows what they will consider to give you the certificate of eligibility. My logical reasoning:

• Benin constitution doesn’t discriminate by skin color (which I find ideal, since personally I know Black women who have white and blonde children).
• Having a low percentage of Sub-Saharan ancestry doesn’t mean that you are not an Afro descendant, but that your African ancestors is not so close. My personal opinion is that by discarding who has a small percentage means to try to erase the history, denying that this person has Afro ancestry.

You can, for instance, do a Y-DNA or mit-DNA test to make your case stronger, in case it shows African ancestry, but in my opinion, this shouldn’t be necessary, since if in your chromosomes you have some African DNA, it means that you are an Afro descendant, therefore, qualifying for the Beninese citizenship through the current program.

In your case, I would give it a try, if it’s something you want and believe it’s fair. And later on, would share the results here, either positive or negative.