Joseph:
I think you're really going to like this hike. It's one of my favorites, a beautiful high-country ramble. None of it as tough as say, Iron Mtn, but it's a lot of miles.
As usual, I'll refer to an
ACME topo map (or "Acme fu" as Rumpled so eloquently put it
).
I would start at the
west Mt. Williamson trailhead ("A"), head up the PCT to the shoulder of Williamson ("B"), hit the heavily travelled use trail heading up the ridge past the named summit of Williamson and continuing on to the true summit of Willamson ("C") then to the unnamed peak at "D."
Note: There is good use trail for sure all the way to "D" which is as far as I went last June on a training hike, but I'm sure that the use trail goes all the way to Burkhart Saddle because the last time I did the whole loop there was a good use trail and because I could see a use trail descending from Pallett Mtn the last time I was at Burkhart Saddle. From "D," continue to "E," then drop WSW to the saddle followed by a climb up to Pallett Mtn ("F") and then a descent to Burkhart Saddle ("G"). From the saddle, follow the very clear use trail to Will Thrall Peak ("H"). It's not particularly difficult, and I think it's worthwhile to continue along the ridge to unnamed summit "I" which is actually higher than Will Thrall Peak. From "I," retrace your steps to Burkhart Saddle "G."
Note: There is a trail shown on the topo map. Traces of a trail do exist and are usable as a way to bypass Will Thrall Pk on the way back. I saw a Sierra Club group using the trail. I myself didn't use the trail so am not sure of the entire route back to the saddle. From Burkhart Saddle "G," descend to the east PCT/Burkhart Trail junction at Little Rock Creek ("J").
Now for the tricky part. The section of trail (the PCT) from the east PCT/Burkhart Trail junction ("J") to Eagles Roost "M" is closed to protect some frogs. Apparently one can be fined if one violates the closure. The route therefore progresses from "J" to the west PCT/Burkhart Trail junction "K" and then to Angeles Crest Hwy at point "L" via Buckhorn CG. From "L" one walks the ACH to point Eagle's Roost ("M") and from there back to your cars at point "A," either via the PCT as it traverses Kratka Ridge or by continuing on the ACH. Unfortunately, I don't know of a way to avoid walking the ACH on the section from "L" to "M."
Comments: It's a lot of miles just to do the basic loop from the west Mt. Williamson trailhead over PVR to Burkhart Saddle down to Little Rock Creek and then back to the west Mt. Williamson trailhead. It's even more miles to add the side trip to Will Thrall Pk and the unnamed but major peak at point "I." Add to that yet even more miles because one has to go miles out of one's way to avoid the closed section of the PCT. I'm not sure how many miles this adds up to, but it's got to be approaching 20. Just something to factor into your start time, particularly this time of year when the days are short.
It's a
great hike. I look forward to your TR and photos.
)
I guess this board is the repository, along with a lot of great contributions of others. I just hope ACME maps stays around for a while and doesn't go away like topozone which got gobbled up by Trails.com. 
