For splitting files to exact sizes, you could always use the command line tool Linux / Unix tool: split. The windows version is here: http://unxutils.sourceforge.net/
Using the tool you can split files to any size you would like, and you would use "cat" to recombine them.
split -b=10090000 bigfile.iso bigfile_part.
To split your files to exactly 10090000 bytes.
Your output would look something like this:
To recombine just do:
cat bigfile_part* > bigfile.iso