I would strongly recommend following the 4wd road from the corral for another full mile until reaching a point that is directly NW of the summit. From there, one can more directly follow a sloping drainage to reach the ridge at a higher point (roughly 9750'). The climb will be more effortful but the overall efficiency of this route seems preferable to me.
In any case, the weather was beautiful and the climb was very rewarding - Sweetwater is such a beautiful area
We then followed directions to Middle Sister - these wisely route the hiker to prefer the west side of the saddle. We could have even ventured further West than we did and had a slightly easier go of it. As others have stated, it isn't a fun push through the mountain Mahogany, but it isn't the worst either. Plan to take a bit of extra time to push through the descent until you reach the rise toward Middle Sister's slope.
Climbing the North slope of Middle Sister we encountered a small patch of hardened snow/ice and were glad to have hauled traction and ax's along with us. Clearing the snow patch took some time but wasn't too tiring. After that it was 30 more minutes of high stepping until the summit.
And what a summit it was. Terrain spread out in front of our drooling eyes in all directions from the mighty Sierra sawtooths to the Northern Sierra to Nevada sub-ranges we've yet to climb. My mind has taken the liberty to return to these views in my sleep last night
From the summit, we saw a use trail heading NNW in the drainage directly West of East Sister and decided to give it a shot. It appeared to be rife with Mahogany, but the trail looked well-used. After reaching where we thought the trail was, we really didn't find clear evidence until it entered the brush. In the end, the use trail wasn't as apparent as it seemed from the summit but did run clean all the way down until meeting up with the 4wd road that would take us back to the corral. Another fantastic day in the mountains was capped off with dinner in Bridgeport and a cool night in the tent at Desert Creek.