Economist John Shea studied how baseball’s unbalanced schedule affects our ability to isolate and calculate reliable Park Factors. Given the range of park factors we usually deal with, some of the variation is strikingly large, and throws into question the worth of traditionally calculated park factors. I’m not sure the difference is worth doing the laborious translation Shea suggests because even then he isn’t taking into account other serious variables (like the weather and injuries) that have a real impact on these numbers.
I think the real message is that Park Factors are a very blunt instrument for measuring how any particular ballpark affects run production, and even blunter when it comes to measuring other isolated effects, like home runs.