Root do i need to inject the parameter file into new boot.img

[androidcustom18]

I unpacked the boot.img, i left the kernal alone, i just modified the ro.secure to make the system rw. Why is the recovery show 32mb but has the same stuff as the boot.img? The new boot.img was generated in a .bak file, can i flash this, or do i need to convert it back to img format?

Edit, made the img file, but now its at 16.5 not 16mb is that normal?