Did you ever do this? I wouldn't mind trying it out if you had success. I have a Macbook Pro mid 2009 and it gets 80c to 90c's when I run Netflix for a while. This isn't a great concern but if I watch a few movies/shows a few times it will add up to several hours a week of hard use. Which may just push my old MBP over the edge.
I've tried using a fan blowing over the top of it, but it drops it maybe 1c. The most effective thing I've done is put some frozen thing under it but that only has gotten it down to 86*c at the lowest. Sure it makes the bottom of the case cold but not the internals. I've also noticed some condensation when I do this, which is what stops me from putting anything frozen near the top where it could suck in the moisture (or even droplets of water.)
I'm trying to make it last another year until college is over (unless the next macbook update is great enough to justify selling mine and buying a new one.) If not I will try and make a good make shift mount for it use a fan and something cold, and run it through a TV if I want to watch something long.
(Ik this is an issue with MB's and wish there was a good praticle fix, I see a lot of MB's running hot for long periods of times every day. Because you know the girls have to watch every season of Gossip Girls in one day long marathon.)
Sorry for never answering

I forgot
I more or less ended up doing it actually. I bought a bottom case for 25€, had a couple scratches but who cares. Then I bought a set of 1mm steel drill bits (2 in the pack for 4€)
I measured out where exactly the fans are opposite of, marked it with a white coloured pencil, drew a grid into the circle. Lines 1mm apart, giving me 1mm squared boxes.
Then I started drilling. Slowly and steadily was the key as i didnt want to overheat the aluminium. It worked well. 1hr and 25 holes later, yes it took that long, the drill bit snapped. Little bit too much pressure and bam.
So I took the second bit, got just over half way for the left fan holes when it snapped too, i was being so careful but still.
As I couldn't be bothered to drive and get new bits, I took out the right fan and put on the new bottom case. i had run tests with 1 fan, having two CPU cores run at 100% each, and compared that too the temps with new case.
First thing I noticed was that the sound from the fan was different. It seemed louder as it was a different frequency

Secondly, temps where no different. But keep in mind, i had only drilled holes for half of the left fan. So maybe when its got more it would make a difference.
I decided to not try the wire mesh thing because the black plastic in the bottom case is to stop shorts on the logic board when it gets pressed against it from pressure when moving it or whatever. Wire mesh would make it short out like crazy, dont need a dead logic board
Maybe the best thing to do would be to just cut a big hole in the bottom and then have a laptop cooler to constantly blow cold air onto the logic board. Ok you could only use this when at your desk and exchange it all the time for the original bottom case as you cant have your logic board exposed. Maybe a sliding doors mechanism would work

. But im not that desperate, haha
Since then the bottom case has been lying in my shelf. Ill carry on with it at one point I guess.
I upgraded my 2010, which is for sale, to a 2012 last week and its quieter, and the fans seem to have a different frequency now, not as annoying.