I put my Z9 at 681 mhz and it wouldn't make it past 12 minutes.   I adjusted the frequency to 675 mhz and I have been running for 40 min at avg. sol sped of 59.26.  Im getting 62.45 sol currently.  Chip temps are at 69c/70c.... I have noticed that the machine LOVES under 72c.  I am pretty sure that the avg. will increase over the next hour or so.  Current temp outside where I live is 50f or 10c...I'm sure this helps too!  GREAT JOB JASON!

I hope this helps the group