Are you saying a tarp tensioner on the ridgeline, the tarp to stakes, or both? And you are talking about tieing to the hammock and not the trees? Have you done this using the stock asym tarp?
Tensioners to the stakes. I don't use a tensioner on the ridgeline. If I think it is going to rain, I will stake the tensioners almost to full extension. This pulls the tarp down on the ridgeline of the hammock. When I get in the hammock will drop a little and the tensioners will still have some tension. This keeps the tarp near the hammock ridgeline and coverage is great. This works for the MacCat and SG style tarps. If the weather is good I just tie the tarp higher.