Mike, you and I are the same height.  No issues hanging the hammock high enough.  You really only need and want to be a few inches off the ground once you're in the hammock anyway.  Any higher and entering/exiting turns into too much of an adventure!  If the hammock is a couple feet off the ground when you string it up, you'll sink down about 2/3 of that distance when you climb in.  Another advantage to keeping it low is it allows you to keep the tarp down lower to eliminate rain blowing in.

I have not had any difficulty finding a set of trees properly spaced in the Q.

I use the Clark and love it, fwiw.  Have not tried the hennessey.