Well, first thing that I'll say, I'm glad to see you're 13 and starting to trap. I hope you're trapping 50 years from now!
I'll tell you, an adult groundhog's head is about 4 inches wide. And nearly 4 inches long.
My 160 body-grips have a 6-inch jaw spread, so you don't have much room for error. If you don't catch the hog behind it's skull, it's going to pull out.
Groundhogs are strong critters, I think a coon would be a little bit stronger. Either way, make sure you have your traps anchored good.
I'll try to explain how I bend my bodygrip triggers. Very similar to a "circle trigger". On small bodygrips, I'll start maybe 1/2 inch down the trigger wire, and bend it out, at like a 45* angle. Then I'll go out, maybe 1/2 inch, or 3/4's of an inch and bend it at another 45* angle down.
Basically, the trigger wires are parallel with the trap's jaws. My theory, I want those trigger wires, out of the animal's eyes.
Groundhogs don't have much of a neck, so what I expect to happen, the hog will fire the trap with it's shoulders. So, you've got it's skull.
Another thing I'll add, in my opinion, one of the main reasons for a body grip being fired and no catch, the trap wasn't solid.