john smith wrote:

It has to be farther back because of the increase in height and
protection of the airspace surfaces. Specifically, a 7:1 transition area
slope from the runway centerline. For every one-foot vertical, you have
to move seven-feet horizontally from the reference. 148*7=1036 feet from
the centerline (minimum). This is all spelled out in TERPS.

Not entirely true. We are getting a new tower here at BIL. It is 40
something feet taller than our current one. It is also only a few
hundred feet off the centerline of one of the runways, much closer than
before.