Thought 1001 Tools would do this, but it just seems to put everything at the specified spacing and make up any difference in the middle.
What I'm looking to do is mainly purlin/girt spacing, where I specify the start and end points and max spacing. For example, purlins evenly spaced over an area, with a maximum spacing of 5'. Obviously a little math, place the start, move it to the end and /whatever-my-math-showed will do the job, but I'd really prefer a plugin that will let me use my own component placed at the start and end locations, (we use several different profiles of steel in similar applications) and will simply copy it however many times it takes to get a <5' (or whatever it is in that situation) even spacing.
Ideally it would also account for the width of the purlin/girt/whatever, (i.e. checking for max spacing using inside-inside measurement) but they generally max out at 2.5", so center to center spacing is rarely going to be a problem. The one-in-24 or one-in-30 situation where it would save one $30-$50 purlin on a $3k or more structure to measure inside-inside is really not going to bother anybody.