I have a tool that is posted here somewhere FDIMAGE that I used for exactly this. It can split images into pieces so you can make it make two 180K files that you can serial transfer over and then recombine them into a full disk.
Usage: FDIMAGE [options] source target
Options:
The source can be a filename or floppy drive (a: or b: ).
The target can be a filename or floppy drive (a: or b: , or nul.
/y will skip target filename overwrite prompting.
/v will verify an operation (the target will be verified, not written).
The source media format is determined automatically, but can be overridden
with /160, /180, /320, /360, /720, /1200, /1440, /1680, or /2880.
The target media format is checked unless the /smfc option is specified.
The /k will prompt the user to press a key before all operations so the
user can swap disks if necessary.
The /s2, /s4, and /s8 options indicate that the source is multiple files.
The /t2, /t4, and /t8 options indicate that the target is multiple files.
/noxms will disable xms memory usage; /noems will disable ems memory usage.
Options may appear anywhere on the command line.
/? will show this help.