[Bug-ddrescue] how to rescue floppy disks?

[fctk86]

hello,

i'm using ddrescue-1.7 in order to backup lots of old 3.5" floppy disks 
and i'd like to make the process as efficient as possible.

as far as i know:
- high-density 3.5" floppy disks have 2 sides, 80 tracks per side, and 
18 sectors per track; each sector holds 512 bytes
- double-density 3.5" floppy disks have 2 sides, 80 tracks per side, and 
9 sectors per track; each sector holds 512 bytes

that said, i imagine i should use --block-size=512 --cluster-size=18 in 
the first case and --block-size=512 --cluster-size=9 in the second one. 
is this correct?

i'm asking because the info manual says a little different thing:

`--block-size=BYTES'
`-b BYTES'
     Hardware block size of input device in bytes (usually 512 for hard
     discs, *1024 for floppies*, and 2048 for cdroms). Defaults to 512.

`--cluster-size=BLOCKS'
`-c BLOCKS'
     Number of hardware blocks (sectors) to copy at a time. Defaults to
     64KiB / hardware_block_size. Try smaller values for slow drives (*18
     is a good value for floppies*).

thanks.

p.s. do you suggest me to use the --direct option too? i run gentoo 
linux (kernel version: 2.6.23)