[cctalk] ST-251 MFM Hard Drive sector size question

I have an ST-251 42MB MFM hard disk drive. The documentation says the drive is 512 bytes per sector.  I don't know if this is fixed (hard sectored) or not. My problem is my operating system (OS/9 Level II) wants 256 bytes per sector.  The OMTI 20C-1 controller can handle that but I'm not sure if the ST-251 can. Does anyone know if the ST-251 can support 256 bytes per sector and/or how to configure it for 256 bytes per sector? Thank you,          Mike