It looks pretty good, the bits hanging down in front of the tires are where the gains will more than likely come from. Hopefully you made the grill block easy to work on, since you could wind up needing to at some point. With mine, I remove part of it during the summer and put it back in for winter. I would either remove the wiry parts in the center or attach some more of your grill block material to it to help lower the dam some more. I can't say whether the wiry parts help or hurt, but they just look like bits hanging in the wind. Are you going to do any testing on them? Let us know how they work out.
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