I put all the gear (TIUs, TMCC, etc) under the layout about the center ... and then installed a 6-track yard over it before I knew better ...
Good reception however for some reason. Maybe it's because they are mounted vertically on a plywood sheet 2 feet off the floor with no line-of-sight obstructions?
What does seem to make a difference is when the batteries in the controllers get weak, but not enough to set off the low battery icon. Putting in new batteries fixes it.
Maybe just dumb luck most of it works most of the time so far is probably more like it