UPDATE and more CHALLENGES
In the first week of October, using the SGS #258208 TVC-TRF05 HT8: Famo MFU and the Multiplex Smart SX9 Flexx transmitter and receiver that come with it, I had
all the FAMO functions working. I had tested and tested each function at every step of assembly. So with great care, I mounted the MFU on a platform between the frame rails, tucked the receiver in away from the MFU, and did some "wire management" with wire ties. I was ready to put the 4 ohm speaker in its place behind the grill and the battery at the back of the engine bay. In fine. Then I went to Scotland for two weeks.
Now that I'm back, none of the FAMO functions works.

I checked the battery voltage, continuity of connections, etc., etc., etc. Suspecting that the Multiplex transmitter was no longer binding to the Multiplex receiver that came with it, I tried re-binding them. Nothing doing! Not even a light on the receiver.
For comparison, I dug out my little "Jeep" that I had set up last winter with the Flysky FS-i6X transmitter and FX-i6. It ran when parked, but nothing doing now! So I re-bound the Flysky transmitter and the receiver in the Jeep and
all works fine. Apparently, a transmitter and receiver can come unbound just sitting with no batteries in either and no other use in the intervening time.
Now I want to try using my preferred Flysky FS-i6X transmitter and FX-i6B receiver to run the FAMO's SGS #258208 TVC-TRF05 HT8. I shall persevere! (Or I shall go nuts with frustration.

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