Well, stage spikes in the hands of an expert are deadly (ZeRo would be one of these fox players). If you are consistent enough, then certain characters should always be stage spiked (Falco, Fox, sometimes Falcon etc.).
Don't do it against sheik or characters like that though. In general these characters are not safe to move off-stage against. Thankfully, most of them are light so usmash will often take it rather early. Going off stage for a uair is also viable if the opponent recovers high, and is a wonderful mix-up. Don't do it often. Dsmash on battlefield has a wickedly weird hit-box as well, and can hit Falcon as he recovers from below the stage, so that is another valid option.
Other than that, it seems most Fox mains like me wait for the opponent to come back and launch them again. This requires mix ups and reads, but seems to be instrumental in mastering for this character.
