I've only been out a few times with my SpinnTwinn (it was a christmas gift this past year) on the AT and agree it is sometimes a challenge to find the right spot to set it up.
With a little extra time spent on site selection you can find a good spot.
I have no idea what your experience with tarps is like, but remember, you can set them up OVER vegetation and small trees - one advantage that i really like about tarping.
If i'm in a really tight spot, i'll simply increase the height of my pitch to draw in the wingspan and enjoy the extra headroom. I use a bivy anyway, so unless I have someone else with me, I'm never too concerned about the tarp not being able to cover me or my gear.
Other solutions i've found is to use the trees around as tie off points for the tarp and create a lean-to or some new fun setup i've not thought of before.
I think the variations of setup is why i'm obsessed with tarping. It's so fun to see what you can do with it.
Best of luck!