Hmm...
My previous ASUS N61Ja benefited from a cooling pad with the bottom opened because it would blow right over the GPU and CPU heatsinks.
The G751, however has a very closed design and seems to suck in air from pretty much any hole it can find and the bottom cover only exposes the memory and storage, which are simply not going to benefit from a better cooling solution.

So at best, you'd be cooling some of the plastic under the heatsinks. Consider that even with your CPU/GPU going at 80 degrees most of the keyboard is cool to the touch so the chassis won't benefit that much from a generalist cooling solution.

Also of note is that said N61Ja laptop was used almost every single day for more than 4 years, roughly at 5-6 hours a day and under gaming stress with games that the laptop was not meant to run. With an open bottom and with a cooling pad it ran HOTTER than this G751JY on its own, completely stock.

Make conclusions.

i made a little test in the past minutes
cooler was a http://www.zalman.com/eng/product/Product_Read.php?Idx=492

furmark with cooling pad (fan off) 69°C
furmark with cooling pad (fan on) 69°C

noise was the same...
so pls dont buy any high-end notebook cooler, the g751 dont use it 😉

Thank you all for your really informative replies!
They seem to confirm that this laptop's design hardly benefits from a cooling pad afterall...
Once again, thanks for your feedback, much appreciated!

i use deep cool m6 cooling pad it has a stylish look fit to g751 color and size.. nice big fan in the middle has 4 extra USB slot and a built in 2.1 speakers which sounds good and has a low fan noise.. (although i chance the fan to a much bigger and better blades gives more air.. i use it as docking station so the mouse, keyboard and and any USB devices i plug it on the cooler, so i only have to use 1 USB plug on the laptop. to minimize my USB sockets from being devirginized (plug/unplug) 😄

It does not give a huge benefit in cooling like 1-2c only, i think.. but i like the speakers and USB ports
- i think it draws air on top not on the bottom, just a guess, cause whenever i turn my ceiling fan, temp drops 5-10c ;D

I've had various cooling pads in the past and they were effective on my first laptop, but the design of my second laptop didn't seem to work with them at all and the G751 is so efficient at cooling that sitting one on a cooling pad would seem a little pointless.

Therefore, I bought a Belkin Cushdesk which allows me to sit it on my lap while lounging on the couch/bed without the worry of the exhausts burning my legs! It's squishy on the bottom too, so nice and comfy.