Do I really need to store the usCriticalNesting variable on the stack for each task if i'm only using the preemptive mode?

When using preemptive mode it seems that this variable can only ever have a vaule of zero when interrupts are enabled. Whenever it is in use (i.e. it's value is not zero) interrupts are disabled and therefore a task switch cannot occur, meaning there is no need to store a copy on the stack.

Or am I missing something...

See this post https://sourceforge.net/forum/message.php?msg_id=4399221

This should be added as an FAQ.