Overwatch Vortex + Hindering Shot - do penalties from the same effect stack?

[HibikiSatsuo]

Overwatch Vortex lets you ready 4 ranged attacks as a full-round action. Hindering Shot is an equipment trick that lets you ready to shoot an enemy just as an ally targets them with a save and, if you hit an do damage, gives them a -4 penalty to the save. Could you ready 4 attacks for when your wizard casts a spell and give the enemy a -16 to their save?

[Wonderstell]

Weapon Trick: Hindering Shot wrote:

Additional Prerequisite(s): Precise Shot, Snap Shot

You can distract a foe at a crucial moment, making it vulnerable to your allies' abilities.

You can ready an action to make a ranged attack against a foe when an ally forces the foe to attempt a saving throw. If your attack hits the foe and deals damage, the foe takes a –4 penalty on the saving throw that triggered your readied action.

From the language of the feat I would say that you would only be able to ready one attack per save. The readied attack is fired at the same time as the ally forces the save, and it wouldn't make sense to be able to make four ranged attacks simultaneously.

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And I believe penalties from the same source doesn't stack.

Avoron wrote:

This comes from page 208 of the core rulebook:

"Spells that provide bonuses or penalties...usually do not stack with themselves."

A careful reading of an earlier section on the same page will show that this can probably be extrapolated to all penalties that come from the same source.

Bonus Types:

Usually, a bonus has a type that indicates how the spell grants the bonus. The important aspect of bonus types is that two bonuses of the same type don't generally stack. With the exception of dodge bonuses, most circumstance bonuses, and racial bonuses, only the better bonus of a given type works (see Combining Magical Effects). The same principle applies to penalties—a character taking two or more penalties of the same type applies only the worst one, although most penalties have no type and thus always stack. Bonuses without a type always stack, unless they are from the same source.

Emphasis mine. So if bonuses without a type always stack unless they are from the same source, and the same principle applies to penalties, then we can conclude that penalties from the same source do not stack.