Oh, by the way, I found it: How does kamma ripen when you die?
Here Ajahn Brahmali addresses the influence of last thoughts (the third type of kamma in the article he’s repsonding to).
I am putting my eggs in whatever basket (pun intended) is believed to be the word of the Buddha through linguistic and historical analysis. 
So if one of the foremost experts like Ajahn Brahmali says that the suttas don’t give grounds for a certain belief, and I can see that by looking at the suttas myself; then that’s what I’ll go with. It makes sense to me that the kamma accumulated over a lifetime would have far more effect that one measly thought before death. So really, someone who has been a good person for many years should have nothing to worry about.