What type of "track" car are you making this into? If you are going to under any type of safety scrutiny I doubt that would work as a harness bar. There are rules about attachment, pipe diameter, and thickness. I'm like 90% positive that brace wouldn't pass as safe for a harness bar. It has been long accepted as dangerous to use for a harness bar. Also, mounting anything to that shelf is a poor idea, its very thin. All the rollbars and cages pass through it in cutouts and mount under on the actual tub. Nothing legal will be attached to the shelf.
Would be a good idea for you to look up the rule books for whatever it is you plan on using the car for. Would be a shame to spend all this time building things that aren't to spec and could possibly hinder your event involvement in the future.
oh dear god dont show up at a track with stock seats and a 5 point harness cut into them. If your strapped for cash by a knock off seat it will be a little safer but still not ideal. If possible look for a used fia certified seat. I know it sounds like im being silly but safety is not something to cheap out on or it will cost you or your passenger their lives. I personally couldnt live with that on the back on my mind.
Rant over, I love the build and remember your best investment on starting out is seat time! Seriously you can learn more on blown stock stock and all seasons with 10 track days then 1 track day and Coil-overs with r compounds! Now bouncing boobies! :bouncin: