I got the OS9 CRC24 running now and can exchange images and correct the checksum.
But didn't test whether it works.
I will upload the new program version to the known places.

@Darky
Since B1F41E and B1F41F define the length of the module, Nomad seems to have changed the module.
Original 26.09a filesize: 12,631,320
Nomad filesize: 12.635.004

3,684 bytes difference.


26.09a module length 00 02 56 74 = 153,204
Nomad module length 00 02 64 D8 = 156,888

156,888 - 153,204 = 3,684

He probably knew what he did...


EDIT:
Be sure using UltraISO for exchanging the navboot. I tried WinISO but it changed the size of the image. UltraISO didn't.