Please don't add items to Layers based only on coverage, it's based on items that were tested to conflict together. We don't want untested information in the table.
You have to wear as many layers as possible (all really over the testing) and then see what conflicts with the new item, but you also have to completely fill the layer, like 2 shirts, not just one.
If it doesn't conflict with anything add the layers you are missing, starting with those that cover part or the whole of the new item or layers that include and have more coverage. Then everything else if nothing is found. If still nothing is found start again to be sure. It's exceedingly rare to find a new item that conflicts with no others.
Once you have a conflict, it doesn't end there. You need to remove the conflicted item you are wearing and then try again in case something else also conflicts, especially if the coverage doesn't match the other conflicting item.
Trying to wear a second copy of the item and more if you can is useful to determine how many items can be worn at the same time in the layer.
To do all that, you obviously need to have items to completely fill all layers stored somewhere.
If that's not practical or too much, then depositing items (2 instances if possible) to Frazyl is the best. Or submit them in the talk page, but there will be delays until I get around to finding them.