Cannot install RRF3.01 RC on DuetWifi: "File is too big"

[resam]

I'm trying to install any of the RRF3.01 RC* firmwares on my DuetWifi 1.04.
I'm currently running 2.05.1 - which installed without problems.

However, when I try to run M997 S0 the PanelDue shows this error message for a split second - before the printer resets:

ERROR: File 0:/sys/Duet2CombinedFirmware.bin is too big

I see that my 2.05.1 firmware bin file is around 402KB, whereas the 3.01RC10 is 489 KB.
Is the DuetWifi board no longer supported, or do you expect that the final release version will fit again onto the Duet2-series boards?

[resam]

Ah, nevermind - should have searched a bit harder on the wiki:
https://duet3d.dozuki.com/Wiki/Installing_and_Updating_Firmware#Section_Upgrading_a_Duet_WiFi_Ethernet_Maestro_from_firmware_2_x_to_3_01_or_later