I think it looks fairly proportionate on you, but I would not go for a 40 unless you intent to use it for travel mostly.
I am probably similar height and build and while I do not own a B, I did try on a 35 in store, and found even that to be far too big for my needs.
I do can imagine it being the perfect briefcase / travel bag and larger everyday carry.
If I were you, I would be very mindful choosing any large tote and think carefully about how you intend to use it. I expect a B40 to get very heavy very quickly.
(I have an uomo cabat from BV that I use occasionally for work trips and it weighs about the same empty as a B40 would. Unlike a B, the cabat can actually slide onto my shoulder when not wearing a jacket but it’s still a total workout when I carry it.)
I suggest you aim for a 35 but personally I would definitely go for a 25 or 30 max for private use, but it would be for leisure as I would never carry H or any recognisable expensive bag to work or client meetings.
Happy hunting