For bridge ground wire I've made a"drill" out of a bicycle spoke. Tap one end flat, file it like a spade blade and drill away. Just big enough hole for ground wire.
My RB800. Refinished, truss rod and fretboard changed, custom Wal-like eight coil pickups. All done at my shop. Next is filter based preamp.
Nice player and great sound.
I took a mold of an original Steinberger pivot plate. I’d need an original lefty pivot plate for taking a mold of a lefty. I guess lefties are even more difficult to find than righties. I coul make a lefty, but for one I’d have to make a reverse version of a righty (quite a lot of work as the plate is concave 3d shape) and make a mold of that before making sellable plates. For even some monetary value for time it’s not worth making as I guess there’s not too many buyers for lefties.
You mount the pivot plate thru the middle hole. A countersunk screw (or bolt if you prefer threaded inserts) and a rubber washer is all that’s needed to mount the plate. The plate svivels and strap mounts to the two remaining holes. Just like the original but with simpler mounting hardware.
Making a carbon fiber instrument is not more difficult than working with wood. It’s just different, in many ways even easier.
If interested, please check out
https://www.talkbass.com/threads/winter-2017-build-off-carbon-headless-bass.1259505/