Goerge, as I understand it the biggest problem with the plats is the size (diameter) of the electrode. The plat electrode is barely a pin prick while the Cu core plugs have a huge electrode. Picture the difference between a Big Chief school pencil and that fine .5mm mechanical on your desk. That pin prick of an electrode gets fouled, or otherwise throws an inconsistant spark while the Cu core throws a large well defined spark.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.