I just wouldn't use a seat bolt. Yes I know some installers who do because it's convenient, but you are reducing the thread count into the bolt holes, thus a possible safety issue. Extremely small chance, but let's just say the seat gets thrown in a wreck, causing an injury. Guess who'll be liable? It won't be Toyota.
Plus it's difficult to achieve maximum ground because typically, you are inserting the ground ring terminal on top of the seat bracket. The ground ring terminal, if at all possible, needs to lie against sheet metal...and again, after you have wire brushed the paint off.
Yes, you may have to run the ground wire longer, but there are always good hidden spots along the sides of the vehicle, either by an existing bolt or by creating a new spot with a self-tapping screw.
Since I'm using 0 gauge wire, thus a big ring terminal, I needed a spot where I could run a bolt through the sheet metal, then secured by lock washer & nut on the opposite side. Difficult to find a spot that wouldn't interfere with anything under the vehicle, but I found one under the carpet, behind the passenger side 2nd row. If you should ever have to run a ground bolt that is exposed underneath the vehicle, always silicone the bolt & nut to resist corrosion.