In order to create RGN with boot.bin only do the following: load RGN with RGN_Tool, ucheck all the checkboxes except boot.bin's one, save it as RGN file.
In order to create RGN with gfwpack-ed boot.bin do the following: load the RGN file generated above, save boot.bin, process it with gfwpack, load boot.bin, save RGN.

As for me I'm using my utility gfw.exe, coz it's not trying to be more clever than you are, unlike RGN_Tool

So I made them for you quickly:
[Only registered and activated users can see links. ]
[Only registered and activated users can see links. ]