There isn't a lot of good info for Pre-tension recommendations on Stack Anchor bolts.
In the case of slip-critical connections, you are transferring the shear through the friction between the plates, and so the pretension must be sufficient to give that shear resistance. In my opinion, the bolts for a stack would be pre-tensioned for a different reason. The pretension would help with the shear resistance, but that's probably not a major concern since there is often enough friction with just the dead weight to resist the shear. In the case of an Anchor Bolt, the pre-tension is more of a fatigue issue. The bolts are mechanically sized to resist the tension (By MecaStack), but if you have cyclic loading then the pretension will help extend the fatigue life of the bolt. The cyclic loading would come from the along and across wind, although hopefully the vortex shedding has been considered properly and the across wind cycles are negligible.
Here is an excerpt from a text book "Mechanical Engineering Design" by Shigley that explains the concept. They don't have great information in here to tell you exactly what value you should use, but it does give some good background on the theory and how to consider it in the design.
There is an ASCE publication called "Wind Loads and Anchor Bolt design for Petrochemical Facilities" that had some guidance on anchor bolt pretension. This is an earlier publication, and the most recent one removed all of the anchor bolt info. We don't know why they chose to remove it, because it was some of the better info that we have found. Here is an excerpt.
In discussing with other Stack designers, many have indicated that they follow AISC turn of the nut method for pre-tensioning anchor bolts
Unfortunately, we don't have a definitive recommendation for anchor bolt pretension, it seems to vary by designer.