An look at homeruns by outfield fly-ball instead of using just "fly-ball" data that includes infield fly-balls. Progressive Field ranks as one of the lowest with regards to inflating homeruns per outflield fly-ball. Interestingly, Petco isn't the lowest, though it is second lowest. New Yankee Stadium has the highest park factor for homeruns per outfield fly-ball.
There's also a little unrelated tidbit in the beginning of the article that I didn't know. The author writes that Fangraphs is inconsistent in their K% and BB% metrics, as they use K/AB for the K%, but BB/PA in the BB%.