Seems that 8192 is a good maximum for region size. Both the viewer and the simulator agree.
To that end, I added Constants.MaximumRegionSize and have RegionInfo enforcing same.
Having a maximum region size is also good for searching for neighbor regions as this limits the search area. This constant is thus used in the ‘find neighboring region’ logic as well as the ‘find region containing point’ logic.
For the moment, this is in the varregion branch of the OpenSimulator source repository.