I see it as any other road/speed differential.
I'll 'take the lane' on a 65mph road only if I am willing to monitor rear approaching traffic. Usually this is not hard to do reliably as there is less to pay attention to ahead on such a road (i.e. no intersections, no pedestrians that may cross any second, good road surface, etc.)

What I will do is see the reaction of approaching vehicles. If they react a bit to me great, I do do and move right. If they don't, I move right at the point of time when I will be out of the path of the vehicle and will move to the position I'd be in anyway if not 'taking the lane'

Now if there is no room to move right (say fog line=k-rail), this eliminates an escape route and I think this can be concerning on a 65mph road. If I must ride such a road, I would certainly take the lane. hugging the k-rail, still the in the potential path of the vehicle would be more dangerous.

If there is a shoulder I may move to it for passing vehicles or if the lane allows just move far right into it. If there is a decent amount of traffic and the shoulder is clean enough and there is a rough/dangerous transition between shoulder and roadway, I may stay on the shoulder.

Al