[D] Firmware • Flash modified firmware on a D-series MIPS?

I have a D6900 plasma (T-MST5DEUC). I have managed to prepare a modified firmware image using a patched SamyGO firmware patcher v0.34 script. The only firmware modification is that it starts the rcSGO script from rc.local at boot.

How do I go about flashing it? The TV doesn't detect it on the USB stick. But it detects the original firmware just fine. The Alternative Software menu option is greyed out, if that's relevant. Is there a way to force the upgrade?

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