I found the concept of a loop appealing - nice to change it up with different scenery all the way down to Boyscout Lakes! Also, this was a great opportunity to take a closer look at the Fishook Arete and the North Face of Whitney for future reference, and get a sense for the current conditions on the MR.
I used the "South Face, Right Side, Class 3 variation" as described by Secor, but in reverse: "Ascend easy talus slopes immediately left (west) of the South Ridge to the headwall beneath the top of the ridge between the east and west peaks. [...] Climb the headwall by following a ledge that rises diagonally to the left".
The key on the descent is to head down the first gully closest to the East Peak - take note of it on the way over to the West Peak. Here's what the headwall looks like from the East Ridge below the East Peak - there's a short chimney section followed by a ramp/ledge system:
This is the short chimney section seen from the top of the ramp/ledge:
And here's the entire headwall with the ramp/ledge system easily visible cutting across diagonally, with the chimney section all the way at the top:
Once you're past the ramp/ledge system, it's smooth sailing down sandy scree all the way to right below the Whitney-Russell Col:
There's a 10 minute climb back up to the col. As Secor points out "This pass is also known as "Whitney Col." It is not the low point between Mount Whitney and Mount Russell, but rather then notch immediately northwest of Iceberg Lake". It can be seen on the picture above right before Whitney's northeast ridge gets really steep. It's Class 2 from the pass down to Iceberg Lake.