Lol, I thought this was a suggesting thread and I was going to post that exact cooler the U2 model. I just bought it to use for my 15" MBP. Love it!
As for your question, I placed both mine near the top left and top center which is where I experienced most of the heat coming through from the bottom panel.
It keeps the bottom really cool now! Also it's great to use on the lap because the bottom has a rubbery soft pad on it so I had it on my lap while doing some homework on the couch. Solid cooler, air holes help dissipate heat and aluminum design is a plus. The 15" overhangs both sides by about .5" on both sides, but not a problem at all.
Only complaint is the USB plug when plugged in the power cord to the fans comes off the from the "top" or I guess the back. Meaning if I plugged it in to the USB port closest to the front, the cord gets in the way of the 2nd USB port. If I plug it into the 2nd USB port next to the mini display port, then you can't plug in a mini display port. There is a built in USB plug on the usb adapter so you'll still be limited to only 2 total rather than a possible 3 if they had made the power cord come off toward the bottom edge...
If I'm confusing you about this, if you look at the amazon picture of the usb adapter, you see where the attachment is on the side? That gets in the way of either one usb port or the display adapter depending on which usb port you plug it in. Not a deal breaker, but this could have added another USB port while one was being used to cool the laptop. Not a problem if you don't plan on using the mini display port I guess since you could just use the usb port closer to it and have the other usb available. okay enough rambling.. let me know if you have any questions!
also I prefer the cooler over SMC fan (which I still use) b/c the cooler is definitely a lot quieter than the fans at 4000RPM.
As for the cooler I use it only at my desk and I always use a USB hub to power it never noticed any problem...