Camera simply boots up as normal with no delay.
The next method would be to test the "Firm Update"-Menu.
Place a file called PS.FI2 on the card and see if the menu-entry shows up. If it does, we would have to find out how the FI2-encoding mechanism works.
Edit: I just read, that the "Firm Update"-menuentry does indeed show up. Now we "just" have to find out how the FI2-encoding works.
Maybe the DSLR-Firmware-decoding-discussion gives us some useful hints.
Another approach would be reverse-engineering of the update-loader in a DryOS cam. The decoding function has to be in there, somewhere. A quick test shows the string "Update File Error!!!". With a little luck it is directly referred to by some function.
Edit2: In the A720-firmware is the Firm-update function at 0xFFDC6538. The decoding should take place in a function called FIRHANDLER, located at 0xFFE2CB20.
Cheers.