A feedthrough subassembly that is attachable to an active implantable medical device (AIMD), the feedthrough subassembly comprising: a) a conductive ferrule comprising a ferrule opening with a peninsula portion of the ferrule extending into the ferrule opening; b) an insulator assembly, comprising: i) an alumina insulator at least partially disposed within the ferrule opening, the insulator comprising an insulator outer perimeter surface extending to an insulator body fluid side and an insulator device side; ii) at least one active via hole disposed through the insulator and extending to the insulator body fluid and device sides; and iii) a composite fill (185, 186) disposed within the at least one active via hole, the composite fill extending to a composite fill first end disposed at or adjacent to the insulator device side, and to a composite fill second end either recessed inwardly from or residing at the insulator body fluid side, the composite fill comprising (i) a ceramic reinforced metal composite comprising alumina and platinum and (ii) a substantially pure platinum fill or a metallic wire, c) a peninsula gold braze supported by the ferrule peninsula adjacent to the insulator device side; d) an insulator perimeter metallization (150, 152) disposed at least partially on the outer perimeter surface of the insulator; and e) a second gold braze hermetically sealing the insulator perimeter metallization to the ferrule. a) a conductive ferrule comprising a ferrule opening with a peninsula portion of the ferrule extending into the ferrule opening; b) an insulator assembly, comprising: i) an alumina insulator at least partially disposed within the ferrule opening, the insulator comprising an insulator outer perimeter surface extending to an insulator body fluid side and an insulator device side; ii) at least one active via hole disposed through the insulator and extending to the insulator body fluid and device sides; and iii) a composite fill (185, 186) disposed within the at least one active via hole, the composite fill extending to a composite fill first end disposed at or adjacent to the insulator device side, and to a composite fill second end either recessed inwardly from or residing at the insulator body fluid side, the composite fill comprising (i) a ceramic reinforced metal composite comprising alumina and platinum and (ii) a substantially pure platinum fill or a metallic wire, i) an alumina insulator at least partially disposed within the ferrule opening, the insulator comprising an insulator outer perimeter surface extending to an insulator body fluid side and an insulator device side; ii) at least one active via hole disposed through the insulator and extending to the insulator body fluid and device sides; and iii) a composite fill (185, 186) disposed within the at least one active via hole, the composite fill extending to a composite fill first end disposed at or adjacent to the insulator device side, and to a composite fill second end either recessed inwardly from or residing at the insulator body fluid side, the composite fill comprising (i) a ceramic reinforced metal composite comprising alumina and platinum and (ii) a substantially pure platinum fill or a metallic wire, c) a peninsula gold braze supported by the ferrule peninsula adjacent to the insulator device side; d) an insulator perimeter metallization (150, 152) disposed at least partially on the outer perimeter surface of the insulator; and e) a second gold braze hermetically sealing the insulator perimeter metallization to the ferrule.