More then 16 characters ?

[Eros]

I have a problema by now. I can´t add a user with more then 16 characters. 
I have made

I have modify /usr/include/sys/param.h       and     /usr/include/utmp.h, and after

make buildword
make buildkernel KERNCONF=( my kernel )

shutodwn now

make installworld 
make installkernel KERNCONF=(my kernel)

mergemaster

reboot


i have try 3 times....and nothing hapennings ...please list help-me !!!!! What do i have do wrong ?