The Pi has a tiny room in the housing, but is secure and stable housing. It is different even with the cover, once placed it firmly closes the housing, so that, for example should be a wall mount no problem.
The heatsink I have not yet been installed because the CPU in my Pis housing 900Mhz overclocked yet been heatsinkless not exceeding 50 ° C heated up, so I can to give any feedback.