The above pic is of the outlier from the Boulder Grove. Its a long hike to get up to see just one tree, but at least it turned out to be 15k volume.

I have now visited the boulder grove a couple times and it is a small enough grove that I think I have canvassed the whole area and measured all of the trees of about 15k or more.  It is a grove that can be explored in a short day with only with a moderate walk.  If you want to see the outlier up the hill it becomes a bit more like a medium hike, however it is not that far up the hill, maybe only about 600-800 feet extra altitude gain.  It is a little bit overgrown in places with underbrush, but not impassable by any definition.  There are no trails however, so figure on cross country hiking weather you are exploring the main grove or chasing down the Outlier.  On the way to the Outlier I did come across an old overgrown road and heavy steel cable from former logging operations decades ago.
 
The largest tree in the grove came out at a bit over 25k total volume and I have measured 4 trees that are over 15k and deserving of the effort.  The outlier is not the groves largest, but it is sufficiently big that I felt the time It took to climb up to it was worth it.  Here are the specs on the four largest trees in the grove that I have measured:

Four Fingers
Base circumference:  72'
DBH:  17.2' 
Height:  261.5' 
Volume:  25,838 Cubic Feet

Three Fingers
Base circumference:  80'
DBH:  19.5' 
Height:  246' 
Volume:  19,880 Cubic Feet

Boulder Beauty
Base circumference:  58' 3"
DBH:  13.6'
Height:  253' 
Volume:  16,224 Cubic Feet

Boulder Outlier
Base circumference:  60' 4"
DBH:  15.1'
Height:  222' 
Volume:  15,095 Cubic Feet

Below are a couple pics of the four finger Tree, three of the Three Finger Tree, and one of the beauty.

And below are some pics of the Outlier Tree for those that may not be able to invest sufficient time and effort to climb up and see it for themselves.