viii: Which marksman scored six consecutive direct hits on the game pie?
x: Who masqueraded as George Wilson?
i: is side-whiskered poet and novelist PERCY GORRINGE in
ii: BOBBIE WICKHAM is called a "carrot-topped Jezebel" by Kipper Herring in Jeeves in the Offing (googled by catsgomiaow)
iii: Bertie's cousins the twins CLAUDE and EUSTACE WOOSTER (guessed by catsgomiaow, google-confirmed by dubdobdee)
iv: The race was awarded to Colonel Briscoe's SIMLA, despite a black and white cat running onto the course and unseating the jockey, in Aunts Aren't Gentlemen (Googled by katstevens)
v: The hat went to MR BUTTERFIELD, in Stiff Upper Lip, Jeeves. (Googled by katstevens)
vi: GUSSIE FINK-NOTTLE, after newts in THE MATING SEASON (guessed then googled by katstevens)
vii: the piano player is FREDDIE BULLIVANT in the story "Fixing It For Freddie" (reluctantly known by non-fan jeff_worrell)
ix: The KID CLEMENTINA from a short story in VERY GOOD JEEVES! (guessed by katstevens, google-confirmed by dubdobdee)