Leo Last: 6DUS Men's Brannock: 7.5D
I own the Diesel boot in 6.5d and the Edward boot in 6d. I can make the 6.5D work fine with full arch support insoles and the 6D in half insole arches. I tried the Brass boot with Floyd last in 6.5d and my low volume feet swam in them.
So, based on past experience with the Leo last I felt confident in sizing for this pair