Tarp size for 1P and dog?

I'm waiting for the bugs to go away so my dog and I can go out with our new GG Spinntwinn. It's the equivalent of an 8' x 10' and, as tested on the living room floor, is big enough. My dog is a 72# 3/4 Lab, 1/4 Golden Retriever.

My dog's pack includes a lightweight breathable dog jacket (Ruffwear Cloud Chaser) for when he's wet (so he won't get my sleeping bag wet) or if it's going to be below 35* at night (he's an indoor dog so if it gets cold his teeth start chattering). I also take a piece of towel and a comb to groom him at bedtime, which solves the mud problem. My dog is part of my sleep system, so I want him snuggled close! Usually he sleeps curled up at my feet and keeps them warm!

Just a curiosity- when tarp camping with the dog, do you do anything to keep him from running off at night? What about predators, coyotes, or distractions like bunnies, etc.? I mountain bike and go on short hikes with my husky when it's cool enough (she overheats if it's above 75F in a hurry) and she wanders about, usually staying withing a couple hundred yards of me, and comes running when I call. She knows that I have her water so she won't go far (in the desert- my water is the ONLY water)…

Here's a "where's waldo" of her following me down a moto trail in our local hills (you can just see her over my right shoulder) –

BM

Yep. I bring along one strong stake (as opposed to the needle types I otherwise use) when I'm using my Shangri-La 3 and hook his long lead to that. I'll do the same with the flat tarp. I'm not worried about predators or him running off but he would chase squirrels, chipmunks, pikas, etc. And worst of all, a porcupine. I'm working on trying to stop that behavior and he's showing improvement. He's rarely off leash but I clip his leash to my waist belt and I don't want to get jerked around if he goes after a rodent.