I've looked up and down AR 670-1, the ALARACT, and even ROTC TACSOPs and found nothing about where an officer places their rank on the shoulder loops of the trench coat (coat, black, all weather). Pointers?

From AR 670-1, page 194, 28-6 section b:


On the Army green and white uniform coats, black all-weather coat, and the windbreaker, officer grade insignia
is worn on the shoulder loops, 5⁄8 inch from the outside shoulder seam, and centered front to back (see fig 28–46).

I'm glad you found it that fast. I've spent the last hour and a half, and this is all I got (from USAPA website):

b. How worn.

(1) Non-subdued.

(a) On the Army green and white uniform coats, black all-weather coat, and the windbreaker, officer grade insignia is worn on the shoulder loops, ? inch from the outside shoulder seam, and centered front to back (see fig 28-46 ).






Figure 28-46. Insignia of grade, other officers, on shoulder loops

I get this question asked alot at my civilian job (Army MCSS) and at my SDF.