I never had an issue at any speed or deceleration with my hands off the bars. Even tested several times right after I got the bike to see if it would do the tank slap with the bars when coasting down from 50. It never did.
At the 5K service, they are suppose to check your neck bearing with there fall-a-way test. According to the test mine needed adjustment.
So the day after the 5K service, I am coasting up to a light. Take my hands off the bars and as I was decelerating at about 43 or so the bras started to shake and by 40 it was violent. Tried several more time and did the same thing each time. Took the bike back to the dealer, as I was not happy.
I learned a few things. One the test for the 15 is different than the 13 and earlier. So that calmed me a lot, as it was not a they typical dealer mistake on the older road glide neck bearings.
They did the test adjusted again, and mechanic test road, again tank slap. Another mechanic did the test, adjustment and test ride, again tank slap. 4 different mechanics worked on it trying to get it right. They finally moved the bars back to as close as they could get it to stock with out the pin, did the test and adjustment and then move the bars back to where I had them. Now the tank slap is 99% gone, been able to get it to do it once in 500 miles.
So the position of the bars affects the test, due to how much weight is behind the neck, move the bars forwards and their is not as much weight behind the next. May also be why the shorter bars on the non CVO RG have weights on their clutch and brake clamps.
I will be interested to see if others who have moved bars have issues. Has me worried as I have 14" Monkey Bars on order. How will they adjust with them?
Why the heck can't harley give a torque spec? You know going down the line they have a set torque for the neck bearing. They do not have time for this bull crap method.