Ok its not strictly the right answer but perhaps it might be easier than remastering to stick em on a USB device ??

If you have a DVD burner it might be easier but there's no room on a knoppix Cd to add anything.... so you'd have to remaster and then that involves taking someything out and the deps etc. which if all you wanna do is install the base LFS is a pain....

Depending how big you might try overburning a CD ??
However Ive no idea how to open and add to an iso9660 filesystem under windows. Under linux its pretty trivial. just open it rw and then copy to it and rewrite it....