When I bought my Hennessy Hammock I did an "overnighter" in the backyard so I would be familar with the set up etc (I would strongly advise you do likewise before hitting the trail). At about 5:30 AM my wife let out the dogs and "River" the 100 lb German Shepherd didn't realize it was me in the cocoon hanging between the trees in the far part of the yard. He starting barking and barking....I called him and when he realized it was me he became overcome with doggie joy and nearly ripped me out of the hammock!
Anyhow I would suggest getting the optional large tarp, as I did, as it will offer plenty of cover for your dog underneath. Have a great time backpacking with your Lab.