By Dave Di Somma, Harness News Desk Logan Hollis is upbeat about finishing an already good week on a high. On Monday Hollis and partner Shane Robertson (Hollis and Robertson Equine Services) were the leading vendor by average at the NZB Standardbred National Yearling sales at Karaka. They sold six yearlings, worth a combined $617,000 including the $220,000 sales topper, a Walner – Destinee Jenilou filly on behalf of Australian breeders Yabby Dam Farms. “Three or four more of our yearlings were close to their reserve too so hopefully NZB will…