Paul, a couple thoughts on Macouns...... They fruit well every year, even if they are not thinned well. They also really cluster up. Due to their short stems, and the fact that they really cluster, they drop as soon as they mature. So, by thinning them they will hold longer. They still drop pretty quick though. All apples will size better if thinned well, especially Macouns. Smaller fruit also is less flavorful.
There really is no reason not to thin, size and quality are enhanced by thinning. Since much of what you are growing is for your use, I definitely would thin. If trees are just for deer, it does help w/ return bloom. Like I said previously to you, try Carbaryl at petal fall a,d about 14 days later if needed. Chances are you will do 2 sprays on Macouns.