He's wearing the size Medium for a regular fit

[41] According to Rabbi Colon, modesty was still a criterion for wearing gentile clothing, writing: "...even if Israel made it as their custom [to wear] a certain item of clothing, while the Gentiles [would wear] something different, if the Israelite garment should not measure up to [the standard established in] Judaism or of modesty more than what the Gentiles hold as their practice, there is no prohibition whatsoever for an Israelite to wear the garment that is practised among the Gentiles, seeing that it is in [keeping with] the way of fitness and modesty just as that of Israel." [41] Rabbi Joseph Karo (14881575), following in the footsteps of Colon, ruled in accordance with Colon's teaching in his seminal work Beit Yosef on the Tur ( Yoreh De'ah 178), and in his commentary Kessef Mishneh (on Maimonides' Mishne Torah , Hilkhot Avodat Kokhavim 11:1), making the wearing of gentile clothing contingent upon three factors: 1) that they not be promiscuous clothing

What is the most important rule of matching shoes, socks, and trousers
Plus, "the girls" will be happy as well as the bust of this dress is great for any cup size and the lined dress can be worn with an assortment of undergarments: an adhesive bra, petals or even no bra