Where to place HorsePal fly trap?

Those of you with HorsePal fly traps–how did you decide where to place it? Apparently the flies it catches like it near water. Is a 100-gal watering trough enough water to count as a fly inducement? The other logical place is near the run-in shelter where the horses spend a lot of time. The distance from the run-in to the watering trough is a few hundred feet. .

Any other tips on placement? I understand that it’s pretty easy to move around, but would like to start in the best place, at least on paper.

I had a home-made version similar to this.

We placed it near the natural water source that happens to be near my turn out and the horses.

I have three. Placed one at each end of the barn about 25 ft. from the barn in spots that are sunny all day. And put the 3rd one a couple hundred feet from the barn near my pond.

All of them are catching the same amount of horseflies, at least 6-7 a day – pond doesn’t seem to make a difference.

Thanks. The first place I’ll try is across the fence from the run-in which is where the horses congregate. Sunny, no water nearby but perhaps it won’t matter.