An Allen-based manufacturer of law enforcement video systems has reached its upper-most height in building its new corporate campus, which is expected to accommodate about 500 workers. WatchGuard Video has reached the most vertical point in construction on the initial phase of its new Allen campus. This milestone puts the two-story, 140,000-square-foot office building near Exchange Parkway and Andrews Parkway on track for completion in April 2018. At full build-out, the $46 million office will…