A little googling found these. Not all are placenames or English though.
These are sixes:
AARRGHHS [OSPD], ARCHCHRONICLER, BERGSCHRUND, BORSCHTS, CATCHPHRASE, DORFSCHNEIDER (a surname), ESCHSCHOLTZIA (a genus of poppies), FESTSCHRIFT, FLIGHTSTRIP, FRUCHTSCHIEFER, HANTZSCHIA (genus of diatom), HERTZSPRUNG-RUSSELL DIAGRAM, KAMPSCHROEDER (a surname), KIRSCHSTEINITE, KNIGHTSBRIDGE (a district in London), KOBITZSCHWALDE (a place name in Saxony), KOTZSCHMAR (a surname), KRETZSCHMAR or KRETZSCHMER (a surname), LACHSSCHINKEN, LATCHSTRING, LENGTHSMAN, MALITZSCHKENDORF (a place name in Saxony), MISCHSPRACHE, NACHSCHLAG, POSTPHTHISIC, SIGHTSCREEN, TSKTSKING, VELDTSCHOEN, WATCHSTRAP, WELTSCHMERZ
These are sevens:
HIRSCHSPRUNG’S DISEASE (OED2), SCHTSCHI (variant of shchi, OED2), and TSKTSKS (OSPD3), TSINAMDZGHVRIANT’KARI (a Georgian village), SCHTSCHUROWSKIA (a genus of umbellifer), NIMPTSCHDORF (a place name in Moravia), and the name Angelika KIRCHSCHLAGER