The incident happened on the second pass. Once the RC pilot knew there was FS activity he had no business being in the air. The airboss failed first by telling the RC pilot it was OK and the RC pilot failed by not telling the Airboss he was crazy. And finally, the FS pilot failed for not yelling into the radio to clear the runway!
I agree, but a go around should be done at altitude, apparently the pilot was made aware of the RC plane and confirmed he was makeing a proper go around which would have been well out of the way. Notice the AMA did not say the pilot should have quit when the FSmade his first pass, but blamed him for not having a dedicated spotter. But most of the blame was to the decision to operate FS and model aircraft at the same time.
But as you say, in the end the NTSB/FAA are the ones who will pass actual judgment. All the AMA has done is try to pass along the facts they obtained from actual interviews and a visit to the site.
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I doubt the NTSB is going to put much fault with the RC pilot. They usually blame the pilot.