Not sure what your current gearing is but when you drop down to the 7th drivers you gear down, so you may want to gear back up. 19-42 is a popular combo to run with the 159 track if thats your case your gonna want to gear back up. shoot for around 80MPH top speed.
with 7 tooth drivers 3" pitch at 8200 RPM
19-39 2.05 ratio 72 pt chain top speed 79.4 MPH
19-40 not recomended
19-41 2.16 ratio 74 pt chain top speed 75.6 MPH
19-42 2.21 ratio 74 pt chain top speed 73.8 MPH
20-41 2.05 ratio 74 pt chain top speed 79.6 MPH
21-39 NR
21-40 1.90 ratio 74 pt chain top speed 85.6 MPH
21-41 1.95 ratio 74 pt chain top speed 83.5 MPH
I run 19-39 on my 700 with a 162PC with standard Avid Extroverts
I ran a set of the Wahl Bros drivers on this sled and then I was given a set of the Avid (regular extroverts). I will say there was a lot less vibration from the Avid drivers. The Wahl Bros worked but sometimes I could feel some vibration from the drivers at wide open. Now between the Avid extroverts and the new PC style avids.......I can't tell any difference. But I feel better knowing the new style run off both nubs.