I connected mine directly to the ground terminal on the battery. (Green knob disconnect type)
I did this as well. In a floor mount battery. It’s just my custom to disconnect each time I put the truck away. I don’t have high levels of trust in the wiring and this works fine for my needs.
I suspect the OP is looking for a more convenient option. Perhaps as much for anti-theft as for fire prevention.
Personally, I don’t see what is wrong with the OPs seat mount idea. As long as it’s wired carefully and cables are protected from abrasion….I wouldn’t think sparks would be a risk.
