One of the things that I've found that I have problems with is when I have to set up in the rain. Normally, I'll set up my hammock first then put the tarp over it. Piece of cake in this situation with getting the tarp centered over my hammock. But when it's raining, I'm not talking sprinkling, I'm talking those big fat rain drops that splat.... When it's raining, I have to set the tarp up first then do my best in trying to keep my hammock dry, off the ground and centered under the tarp while I also try to stay under the tarp. I found that in perfect conditions in my backyard, that I still had problems setting up my HH with the HH tarp. I've also found I can set up my homemade huge tarp anywhere under just about any conditions (barring gale force winds) and then set up any of my hammocks under it and not get wet. If it's a bit off-centered, it doesn't make any difference cause my hammock is still dry in the morning. And I've found that being off center is actually usefull because I'll hang my pack on the hammock side with more tarp overhang.
These are just my observations with my homemade tarp (about 11'x11' cat. cut) and the reg sized HH tarp and the XL Clark tarp. Oh, one thing about the Clark tarp, I've never gotten wet in my hammock with it. But when it's in storm mode, I feel like a taco. There's no extra space to hang my backpack to keep it dry.