Do Miss Chances Stack?

[shatner]

An unrelated question I have that I'm wondering if you guys know the answer to:

Say I have two W1S1 casters communion slaved to a W2F1S1 communion master who casts Acid Rain (evo 4 - W3F1). The spell requires W3 to cast and the slaves would have an effective W2 each (native W and +1 to all paths for fatigue purposes from 2 slaves) so they'd suffer 2x the fatigue of the spell (base 30 x2 = 60) divided between the two of them plus whatever fatigue the master incurs (even after reading Baalz communion guide I'm still a little shaky on how spell fatigue is divided among the slaves and master(s)).

However, this water spell also requires a single path of fire. Does that further add to the fatigue cost? If the communion slaves or communion master had F2, would that reduce the fatigue cost?

For multi-path spells, other than the spell's description, is there any way to tell which path contributes to which +/-? For example, a spell might have range of 20+, damage of 15+, 3+ number of effects and fatigue of 30-; how do you know whether it is the primary or the secondary path which effects which + and -?