So How Big is the Universe?

One question that is likely to come up is how big are the Highlands? How far do the Wilds stretch from Earth?
Humanity has had the Barnes-Gutierrez Hyperspace Engine for just over a century. Theoretically if someone left the Solar System the year the B/G Engine was invented and had traveled constantly for that whole time they could be over 9000 light years from Earth. In actuality the span of mankind's explorations are just over quarter of that number.
It is generally agreed that the Wilds encompass a diameter of 5000 light years. Of course the Milky Way itself is only about 1000 light years thick, so that it is really only meaningful to speak of the Wilds in the band of stars extending either toward Sagittarius and galactic center or in the opposite direction toward the galactic rim. The 1000 light year diameter sphere of the Highlands encompasses the entire thickness of the galaxy. Beyond there is only the Galactic Halo region, an area of gas and the occasional rogue star.
The Midlands are considered to consist of a flattened torus 2500 light years in diameter, a distance also only meaningful in the band along the galactic disk.
Every year the border of the Midlands moves twenty-five light years into the Wilds. This is effected primarily by Midland planetary governments suppressing piracy, imposing the rule of law-and-order, often brutally, and opening up worlds which have been isolated to trade and outside scrutiny.
Likewise the Highlands encroach on the Midlands primarily through political and industrial action at a rate of about a dozen light years a year. This is done by voluntarily incorporating worlds into the Great Human Union and tying them to the infrastructure of the Highland worlds. This is most often done by extending Blue Highways to worlds just outside the Highland borders. Soon Major Routes, with their more extensive superstructure and hypercable transmitter stations replace the Blue Highways and the previously independent worlds find themselves with a seat in the Highland Parliament and under the jurisdiction of a Highland Count or Countess, at least as far as offworld interests are concerned.
Those that resists soon become backwaters. It is a rare world which can resist the services of the Grand Postal Service and Department of Roads, institutions which tie humanity together.
Since incorporation into the Grand Human Union is the overt temporal agenda of the Church, a decision whose reasons are based on social justice criteria and prudential moral ethics most worlds face a great deal of pressure to join the Union rather than maintain independence.
The system is not perfect and from time to time a world will resist, but over a longer duration the benefits of membership simply overcome most resistance.