The poly fill doesn't have the same qualities as fiberglass, according to a thread somewhere. You might lose some bass response.
Not sure what you have in Mexico (or in the speakers now), but pink fiberglass is very common and inexpensive to the north.
There are discussions on the web as to restuffling the box. Seems changing the amount can help. I'm not near my files...if I even made a note of that info, but a discussion of this issue might bring up some food for thought.
That's all it is, so no problem.who has never soldered anything past some simple wiring.