So ... adding a washer atop the lid mitigates the stressor point that the carriage bolt "teeth" would otherwise create, is that correct?
And then there's the plate you added to at least the red one?
Hold on tight because I'm not very good at explaining things and there's a lot of things going on with this taco mess. If you remove the taco assembly and look closely at the bottom of the shell, the teeth on the carriage bolt extends past through it and protrudes slightly that it will come into contact with the lid holes. This alone creates 2 problems. It deforms the and creates downward sharp jagged edges on the taco shell. This is the portion that comes to contact with the lid. The bottom of the shell should be always flat and smooth. With the bottom of the shell deformed, it will eventually damage the lid porcelain. A workaround this issue is to grind off the teeth on the bolt, photo below. The teeth are unnecessary once you use a regular nut. You'll be able to tighten the nut without the bolt spinning. You can reuse the carriage bolt or replace it with a ss version which I did on some of my tacos. You'll be using ss washers and bolts anyways so you might as well replace it also,(LE oddly enough has a larger metric ss carriage bolt). Actually a longer bolt is better since it allows the use of multiple washers, a 1 1/4" and 1/2" washer inside the lid.
I don't have any high heat fiber washers so I've been using ss fender washers between the shell and lid instead. The washer are 1" and trimmed on the outside perimeter. The use of a fender washer instead of a fiber will allows you to tighten the nut very tightly without having to worry about damaging the lid finish. The key here is to deform the washers to follow the slight curved contour of the lid. Just place the washer on a 2"x4" and slightly hit it in the middle with a peen hammer. Make adjustments as necessary until it mimics the lid contour. Washer should be sanded and polished to eliminate any sharp edges that may come into contact with the lid. Also not all washers are not created equal. Some are slightly thicker than others. I have a caliper but i never bothered measuring it. Use the thinner version if possible. The washers i get from lowes and at a specialty fastener store tend to be thinner than those from home depot.
I've tested my lids by holding on the handle very firmly and abruptly flinging/swinging it around etc without any damages. That's something i wouldn't dare try on any welded lid handle. Not exactly really real life situation that a lid should ever encounter, but it's a peace of mind knowing that there wouldn't be any problems down the line through regular day to day use.
At some point I'll start a thread on this taco reshaping as i have quite a few members asking for a detailed instructions. Don't have anymore "fresh" taco to reshape. More of a centralized thread as I've been replying on the same things on 4 or 5 different threads.
R: standard carriage bolt.
L: teeth has been grinded down.
Outside edge of washer trimmed.
This is how it looks with the trimmed washer. Should've trimmed it a bit more.
Washers are barely visible