Using a MacBook on its "back"?

Hello everone. I have a MacBook, purchased in Aug 2008, so its the plastic bodied one, 2.0 Ghz etc (the cheapest one). When I'm in my room i perfer to use the laptop hooked up to my external mouse, keyboard, and monitor and I keep the laptop folded and on the keyboard drawer of my desk (the keyboard is on top of the desk). What I do is use InsomniaX, shut the lid flip the macbook so its sitting on the screen side plug in my stuff, and then redetect displays and everything is fine. I was wondering if there are any "problems" with my doing this? Perhaps I should sleep the laptop before and after flipping it cuz the hdd is running? Perhaps sitting the laptop on its screen is no good? Offer your thoughts/comments, thanks I flip it upside down so that the "bottom" is exposed to the air and wont get as hot.

 

does the "cooling" component of having the macbook flipped over make much of a difference? its less convientent to flip it over all the time, especially if I get a video chat invite.