The only time I've ever used a thermo on BS chicken breast was when I first got my thermapen. It was dry as all get out.
Never again. I just went back to the tried and true method.
I cook mine direct over medium to medium high heat. 1/4 turn once to make it pretty then flip it once to finish.
Chicken has a grain to it. Take your tongs and grab the breast about 2/3 of the way to the top or thickest part. Pick it up, turn your hand over so that you are trying to break the smooth side and try and break it in half by using the grill grate as leverage. Don't actually break it in half just bend it enough until you can see it would separate if you wanted it to. Just be sure you're trying to break it along the grain of the meat, you'll want to bend it slightly diagonal, not just straight in half.
I don't care what anyone tells you about manhandling your meat and pushing out the juices. This method works, and it works every time. Every and I mean every time I make chicken breasts (which is weekly) my wife tells me she can't believe I how good I can cook chicken and how juicy it is.
Disclaimer, I'm not a burger smasher either. Just trust me once will ya.
On edit: To the OP. I'm not trying to dispute your method. As always there is more than one way to skin a cat. This is just what works for me, so in an effort to help those chicken breast challenged I though I'd throw my method into the discussion. No offense intended.
"I can get a good look at a T-bone by sticking my head up a bull's a$$, but I'd rather take a butcher's word for it". - Tommy Callahan III
XL Big Green Egg, 22.5 Weber OTS, WSJ Gold/Mini WSM, 18" & 22" WSM, UDS "No.8"
Flyers Orange Thermapen
Napkin Killers BBQ