remastering - isolinux/boot.img file

I've been reading the remastering guide I could find on the internet but could not find howto add/change the boot.img file adding extra boot options via syslinux.cfg to add memdisk and new options for booting memtest86, fujitsu,maxtor,etc.. (hd diagnostics), windows bootdisks (win95->) and dban to make it a little more like a "admin/repair toolkit" and completely eliminate my floppy collection.
The problem is I have a couple of stupid questions from a relative newbie to linux.
I know howto mount the img file through "-o loop". Is there either a way to mount it rw or how do I re-image the "boot.img" file properly as either 1.4mb or 2.88mb floppy?
dd? Or do I need a floppy disk to (re)create the image again?

do I need to edit the syslinux.cfg file with vi, kate? Does it matter?

And does anybody who has done this already have any other pointers??


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