According to Summer Breeze who has had it installed all summer it works. I have a feeling it will work even better without the stock splash guard installed. For those that may not know I have the StickerDick fenders which were like the second ones that were installed, the full fender not the bobbers.
I have been told that not that much air gets through the holes in the stock splash guards, but I would think these vent would work great on a setup where the they have been removed like yours
please keep us updated - might just push me over the edge to remove the splash guards - cant afford the sticker dick fenders and have been afraid that in the rain it would suck without the splash guards, but if these vents really work for you then I might be willing to trade getting slashed the few times it rains for being cooler in our 4 months of 100 plus heat