In 93 I had yields in the 60-70 range and I could actually get the variable speed ground drive darned near full speed in 2nd gear with a 635n head on the 105. Felt like I was flying and I wasn't even hitting 3 MPH. At the time the guys who had 7700's with six row heads couldn't go fast enough to keep the combine full.
Back then good average yields were in the 135-150 range. Jim