So I know how long the temp probe (Maverick) is and aim for the meat's middle, or reasonably close to it, cognizant of not hitting the cooking grate.
Cooked a "dual layer" pork tenderloin: Bought one tenderloin, opened the package to discover it was cut in half. So, no stuffed tenderloin was going to happen.
But that was plan and had the sausages thawed ... as I fork-poked them (to accept marinade) the skin easily tore and I thought "screw it, I'll lose the skin and deal with lose meat."
So, I placed some of the "stuffing" sausage on top of the 1st tenderloin piece and placed the 2nd tenderloin piece on top and cooked "a sandwich".
Lacked string and couldn't tie it ... so, didn't turn it.
Anyway ... back to the probe. I put it in the top one and when I got to 140 I pulled the probe and put it in the "bottom tenderloin" ... 132. Pulled the whole thing when that one said 140.
Here's the "sandwich" at rest, the top had fallen off the bottom a little.