[CentOS] PXE Booting floppy image

Anyone know the correct syntax for specifying a floppy image in the /tftpboot/pxelinux.cfg/default file?

I am trying to use:

label Dos Bootdisk
        MENU LABEL Dos bootdisk
        FDIMAGE discimage.img

But when I select it the menu, I get a message saying "Automatic boot in 30 seconds" and nothing happens.

I would use:

label Dos Bootdisk 2
        MENU LABEL Dos bootdisk 2
        kernel memdisk
        append initrd=discimage.img

but this is a 2.88meg floppy and memdisk wont boot it?

Thanks!
jlc