i installed my jdm front stainless steel door sills today. i think i know why japanparts listed these as "non compatible" with the sti's door sills. the sti's ss door sills are clamped down to the plastic sills by tabs that are attached to the ss piece. i took the whole door sill assembly off and lifted the tabs to remove the original ss door sills. the jdm "subaru" ss door sills are held down by double sided tape and do not have the tabs to fold into the plastic sills. here are som pics for reference.
rights side view of the both installed.
driver side
left rear
