Chin implant a year after sliding genioplasty? (Photo)

Had my chin advanced by 8mm last year, (intraoral incision, fastened with a cruciform 1mm titanium plate & 4 screws). But I still feel like I need about 6mm or so additional advancement, probably with a medium-sized implant of some kind. Unsure, however, of the type & method (silicone, medpor or something else) that should be used for a job like this, taking into account the scar tissue & existing hardware. Haven't yet been able to find any surgeon in mainland Europe who does this sort of thing.