[X25]

This is one of those cases where you either go all in, or not do it. A six point will require harness bar, and a proper seat. An improper setup can crush your bones, or even worse, your balls.

I do have a full 6-point setup on my Miata, and doing the same on Camaro would render rear seats useless, which is not acceptable.

I'm personally planning to just use Scrotch 4-point ASM. ASM stands for anti-submarine. One side of the shoulder belts is double-stitched, and those stitches pop up during a serious accident, letting your body fold on that side before submarining can occur. I think this is a good compromise, and can be easily installed on both sides without any extensive modification. Keep in mind, you should still use a HANS device. If the accident is not serious enough to pop the stitches, your neck could take more than its fair share of the load without a HANS device.