Yep of course, I went off the rails there suggesting any metal washer was a possibility. So the flat non-conductive washers are a hardware store item, or they are something AES has also, or? Sorry if this is dense but I've used 2x shoulder washers in the past on a standard (short) bushing Switchcraft jack to isolate for a footswitch circuit, thru .09 aluminum and 1/16". The nut tightens, just barely though. Obviously long bushing would be better but this was a type 14 jack that doesn't have any options. If there's a better way I have to know! This doesn't seem to be documented anywhere. Or not obvious to me anyhow.