Here's my version for my Hennessy setups...
I use the JRB Tri-glide w long webbing 'kit'; it allows for different tree girths. I place the 'biner (Camp Nano 23, natch) through the loop end of the webbing and run the Spectra cord from the point the wrap leaves the descending ring to the 'biner and back again a couple 'o times, with the obligatory double half-hitch at the ring to finish it off. Doesn't take long to set up and it's ROCK SOLID.
I must admit however, to an obsessive need to over-engineer some things just on principle...