The modern NetBSD kernel is is over 30MB and around 10 to 13 MB compressed in size on i386 and x86_64. So idk were you are getting its going to run in 8MB of memory without major swap slowdowns if it boots at all.
>>zokula+(OP)
That's why I said you'd probably need to use a GENERIC_TINY kernel, which is "supposed" to work on 4MB systems.
Now, it's entirely possible that even with this minimal config it'll take up too much space, but it may work. I got NetBSD 8 to run on a VAX with 8MB of RAM, although that kernel has many fewer drivers/modules.