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 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 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 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 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 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. <EOS>