Even Lehigh Lafayette attendance is down. It was 19,300 at Taylor Stadium with a couple thousand temp seats on the baseball field(later parking lot). When Goodman was built there were 1,000 Aluminum seats underneath the Scoreboard. And they brought about 2300 temporary seats for the South (entrance) end of the Stadium. I remember those first years fans were even able to do the wave.
Then, around year 2000, the below scoreboard seats were moved to the pre-Ulrich Fields Soccer Fields. (a couple of years ago they disappeared entirely). Then the temps disappeared. Now attendance makes at 16,000. Even when Lehi-Laf was for the league title and the playoffs (like 4 years ago) temp seats were not brought in. I suspect no longer using temp seating has cost us maybe 5,000 in attendance over the last decade and a half.