The question is not "would you allow FFM to change any parameter of a spell" but "Is Size equal to Target", as Ezzelino perfectly understood.
What happened: Ladyphoenix assumed that FFM allowed him to change the Size of his spells, having a spell whose target is Group gain a +1 modifier for size.
I told him that, by the RAW, this was not the case ("You may raise or lower the casting level of the spell by five to raise or lower one (only) of Range, Duration, and Target by one step") and that allowing it to change other parameters, such as Size, needed the approval of the Troupe.
He countered by saying that a change of size was a change of Target.
So the actual question is, in fact, do these 2 spells have a different Target, as defined by the rules:
Range: Voice, Duration: Sun, Target: Individual
Range: Voice, Duration: Sun, Target: Individual, + 1 Extra Size, + 1 complexity, + 1 unnatural.
To me, the Target is the same (Individual), and the extra size is one of the numerous modifiers that may add to a spell's level. To him, it isn't, and we actually have 2 different Targets here.
IMO, he's perfectly free to ask the troupe that FFM may vary any or all of the other parameters of a spell, such as base level (for General Spells), extra size, complexity, moving image/sounds... but, by the rules, these are not part of what FFM can affect, and he shouldn't assume otherwise on his own.
Unless, of course, one can provide from a rules a quotation such as "adding extra magnitudes for size are considered a change of Target", or "Size and Target mean the same thing"