Thank you for considering the needs of men who want/need to wear a bra to support their breasts.
I tried to post this before my "one other thing" post, but something happened.
I measure 46B. I echo the other comments, although I have never worn a racer back bra. Here are the things that are important to me: encapsulation cups instead of flattening or minimizing, front close and front strap adjusters (I can't reach behind me without pain), cups that are perfectly smooth (my leisure bras have stitching up the center of the bottom half of each cup that shows under Tshirts and can give the appearance of a second pair of nipples), stretchy cups to accommodate one breast being slightly smaller than the other, wide set cups (I have a good 2-3 fingers of space between my breasts - no chance of cleavage for me
), side support to keep the breast tissue/fat under my arms from bulging, fabric that won't make me sweat, padding under the front closures so they won't irritate my skin, a wide bottom band so it won't roll up due to my high tummy, enough arm hole room that the top of the bra will not chafe my underarm, and colors/patterns/textures that won't show through shirts.