Notes
First run with 920. Interesting thoughts as I observed HR. Mostly 110-120 on the way out (down), didn't get much over 140 even going up the biggest hills, around 130 on the way back (up). Hmmm. I seem to remember 150-155ish being normal last time I monitored HR, 10 years ago.
Cadence was a pretty steady 180 most of the way, 175 late on the way back. Not sure yet what to make of ground contact time and vertical oscillation. Looks like that doesn't show up here, alas. I'll have to look at Garmin Connect.
Used GPS + GLONASS, accuracy should have been improved relative to 310. Maybe. There are still some obvious errors on the outbound leg. Elevation was pretty accurate in terms of change, I think, but it has a DC shift (barometric).
Left posterior chain kind of unhappy on the way back, gotta keep an eye on that.