Chain tension thoughts...

[hiero]

speeddog's got it

I used to be real anal about how I did my chain tension, now I sit on the bike on a rearstand, bend down and go by how the chain feels...

[Speeddog]

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It seems to be consistent with rear wheel rotation, so maybe it is the carrier?  Maybe it is the cush drive hole locations?
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mitt

That's gotta be the carrier.
The carrier is on it's own bearings, so the cush drive holes shouldn't have an effect.

[Augustus]

I think the techs know what they are saying for the average rider in average circumstances.  I would follow their advise and do it to spec. unless you have a mitigating circumstance that requires something different.