Not sure who else has done something similar before, just thought I'd throw it out there...
I was using whoopie slings and marlinspike for a bit. Then somebody showed me a neat trick from another suspension of similar design that headed me in this direction: I use 2 toggles (one for each end) made from 7/8" diameter hardwood dowel, cut to 1.5" long. I drilled a 1/8" hole perpendicular through the center and run my 7/64 amsteel line through it. I have one end of my 5' amsteel suspension line larksheaded to the tree strap (which has a loop at each end) and a backsplice at the other end to stop the toggle from coming off. I wrap the tree strap around the tree, running the suspension line through the other loop in the strap, down to the hammock and placing the fixed loop of the hammock over the toggle. Slide the toggle up and down to adjust the sag and then throw a half hitch around the toggle. Holds tight, trades the marlinspike out for the half hitch and doesn't jam. I weigh 180 and started out using 2 half hitches, one on each side of the toggle (clove hitch) but found a single half hitch held.
I like it because I can bundle my hammock with OR without suspension (using a 'biner on the free loop of the tree strap to bundle suspension with hammock, similar to cinch buckles). It also reduces the bulk of suspension when bundled, since its a single line, not doubled like the whoopie. I also get a little more versatility in diameter of trees and spacing.
Ive been using them for about a year now, several weekend trips and a good 5 day hike with rain... it just works for me.