how long is a pace?

As has been pointed out though, those spells which give ranges in paces are Voice spells where the ranges are, really, guidelines for play. Whilst I find the idea that not everyone's "individual" is the same for any given form, having the variation be linked to leg length seems flawed. Would a permanent limp hinder the size of rock you can summon? Is the new combat tactic to be to hack at someone's knees?

Voice range is tricky enough as is - what happens when a magus casts PoF standing next to a cliff which generates echos? (Other than an out of control firestorm and possibly some inspiration for research?) Does it increase the range?