The times were as follows. I timed each video twice. To try and be accurate.
665-
Cut 1- 4.0 and 4.03
Cut 2- 3.7 and 3.75
Cut 3- 3.69 and 3.60
Cut 4- 3.60 and 3.65
681-
Cut 1- 3.0 and 2.9
Cut 2- 3.07 and 3.09
Cut 3- 2.94 and 2.96
Cut 4- 2.81 and 2.74
That saw in 65 cc form is a strong saw. With a 24" in a 20" Cant at the last GTG it pulled solid 17-18 second times. There was saws much bigger (460, 660, etc) that were between 15-17 seconds).
The 681 picked up about a second over the 665. Which is about par for the increase in displacement. 16 cc was added (about 25% gain in cc).
The 665 only had about a half dozen tanks on it. Where the 681 only had a couple heat cycles and a few cuts (half a tank).
I was pleased with the results and my next test will be in a 20" Cant.