this could be true monty, thnx.
And also....
From what I can tell, those models do not use a separate bootstrap file when loading an image file.
You can try without.
Or you can use the infomir wiki site and open the file release for those models (r23 release). Check if a bootstrap file is included in that release for those models.
Remember thou, that each release version would also have it's own dedicated bootstrap... in otherwords you can not use a bootstrap file that comes with the mag254 r19 release with the mag254 r23 release.
C/P from infomir...
Bootstrap - is startup file that is used to load image into RAM.
Used for updating from bootloader to STB models MAG250/254/270.
It is also used for system recovery of STB models MAG-256/322/324/349/351 and higher.