I didn't detect any ill effect in any performance. As far as down force. I did get 20+ degree heat decrease and didn't spend a dime. I don't think the performance was decreased at all. I run a 10.5 and didn't need to cool it. Tried it mainly just to see if it helped any and it did big time. Both motor temp and ESC temp. 6.5 I think a fan would be a good idea but I would add in the vent cuts just to help. It worked and helped a lot.