The SI1520 tends to produce a lot of heat. After a few minutes, using it on your lap becomes impossible due to excessive heat.
Notebook coolers are nice gadgets, but most of them cost a lot of money, they are heavy and loud.
Here is a nice alternative: Vantec's LapCool 4. There are two versions of this cooler, one with code LPC-420 or 430, which is not suitable for our needs. The other, coded LPC-402, is great: it is cheap, it has a cool "X" shape, and sports a single fan with a diameter of 160mm!
This is important because it allows the cooler to move a LOT of air in a very silent way. Its noise level is only 16dBA, which is soft and gentle and barely audible.
It's a very basic cooler: it has no extra USB ports, it has neither a selector for fan speed nor an on-off switch. It's just a huge fan with an X-shaped plastic shell around, but its lightness makes it very transportable, it's cheap (I paid 15EUR for it), it has the same exact dimensions of the SI1520 and does what it's designed for.
I have no accurate temperature tests to demonstrate the efficiency of its job, and can't confirm if it actually cools the internal components of the SI1520, but it definitely keeps the external shell and keyboard touchable. And, since the SI1520 has a lot of apertures on its bottom side, the cooler definitely sends air inside it (it can be felt exiting the aperture on the laptop's right side) so I suspect that it somewhat cools the inside of the notebook too.
Anyway, it's a small investment which can help protecting the SI1520 from overheating, and prolonging its lifespan.