Which kernel are you patching (distro and version)?
Why do you need 16K stacks? Are you trying to get some binary driver working?
IIRC the old standard was 8K stacks.
Have you read up on why there has been a switch to 4K stacks? See: http://lwn.net/Articles/84583/ for some info.
I noticed there is a patch for increasing the kernel stack size to 16K included with the source code. I haven't been able to apply this patch. Maybe my syntax is wrong. Please advise on proper syntax to apply this patch. TIA