I'm having issues where the amp is going in to protect mode to early.
I can only find wiring diagrams that show a 4 ohm load and a 1 ohm load.
Those are what high impedence speakers are for, you can run way more 8-ohm speakers to the same amp than you'd be able to run a lower ohm speaker.
Wiring any Skar Audio subwoofer or amplifier below 1 ohm will automatically void your warranty on the product.
But without knowing precisely what amp and subs you're referring to, we can't help you with accurate advice.
The box was filled with Poly-Fil to enhance the sound emitted from the sub box, as well as optimize the subwoofer's performance.