@Greenlaw: I also think the bottleneck is on the HDD...
I had already some dropped frames troubles sometimes with the 4 cameras but not at such level.
I guess the 2 kinect require more from the HDD than the 4 cam, yes.
Unfortunately, with the kinect there is no possibility in iPiSoft for data compressing or frame rate decreasing...
I do not use a laptop but a 2 years old iMac, with a classic integrated HDD (unfortunately not an SDD).
I will also try to defrag it, check the system cache localisation...
The problem with an iMac is that I can not simply add another HDD and I do not use my usual PC desktop because it is supposed to be less powerfull and also because it is much more difficult to move to my recording local! ;-)
I perhaps need to think about a complete upgrade of my hardware... but better when iPiSoft will support 4 kinect ! :p
TY Greenlaw for your advices.