Bringing utilization down to 8.9% puts you under a certain threshold, but in your case, I don't think it'll make much of a difference since your total UTI is at 4%. I am in the same boat. I would test and see if dropping both under 9% gives you a boost in score or not.
Welcome, @Anonymous. 
Individual card utilization is determined by the card with the highest utilization. The general scoring wisdom is that the revolving portion of your score is at its best when:
Overall utilization is at 8.9% or below.
Individual card utilization is at 28.9% or below.
There have been some exceptions where people had been dinged before reaching those thresholds. It's possible that some profiles might see an overall utilization ding at about 5%, for instance.
The bottom line is that it looks like you're in great shape. I think the odds are against gaining points for lowering your individual card utilization to 8.9% or below, but you wouldn't know that for sure without testing.
My feeling is that you don't want to inconvenience yourself and that you should continue with your current plan. The reason to bring your numbers down would be if you felt inclined to test so you could see for yourself. But that's going to happen naturally over time anyway.