fsbext allows to rebuild the fsb files, it's an experimental way and not much simple but seems to work very well.
this command will create the file output.dat needed for building the new fsb:
Code:
fsbext -l -s output.dat input.fsb
the following is the command to build output.fsb:
Code:
fsbext -d c:\input_folder -s output.dat -r output.fsb
where c:\input_folder is the folder where are located all the files you extracted the first time included the one you modified.
I didn't test the reimporting of a genh file so don't know or don't remember if it works correctly.