I have found that 5' tree straps work 95% of the time in Florida. They will go around an 18" diameter tree.
Your method works fine but realize that once in a while you will want to hang between trees that are too close for all that suspension. In those cases, simply use a trail stick to create a marlin spike up against the tree and hang the whoopie on that. The reason I mention this is that you want to make the loop in your whoopie big enough to go over the marlin spike.
To hang even closer, skip the whoopie altogether and hang the continuous loop (attached to the hammock) on the marlin spike.
See you in a few days at the Florida Hang!!
"Life is a Project!"