A picture is worth a thousand words sometimes...
I have included my set-up below as you can see. It's not a JRB tarp but the idea is the same.
Back on Xmas Eve I had the tarp edges down tighter to the hammock and suffered a condensation issue too. Thus last night I slept in it configured like this. I set them ridgeline to ridgeline as yoou should notice in the last picture so that when I crawl my bottom in and the hammock takes my weight there is actually a couple inch gap that forms right now.
In case you have not read it before, tie your tarp seperate from the hammock so you can adjust for the gap when you weight the hammock. The first picture shows how I had the wings set. Ideally you should drop the windward side down as close as you can and leave the lee or windless side open so that air can circulate and remove the warm moist air of your breath and body.
Slept in this down to 30 degrees last night and only caught a chill about midnight which was easy to fix by adding a 200 weight fleece pull-over to my polypros and wool socks. I'll be out again in this tonight seeing as how the weather man says a low of 24-25 and that's close to what I want to achieve with this set-up.
Hope this helps!