BDs have an intentionally low standover so I would size the frame strictly based on TT and what bars you plan on using.
I ride a 58cm LHT and would ride a 18" BD.
Yep, I ride 57-58cm bikes, my BD frame is an 18".
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"Let us hope our weapons are never needed --but do not forget what the common people knew when they demanded the Bill of Rights: An armed citizenry is the first defense, the best defense, and the final defense against tyranny. If guns are outlawed, only the government will have guns. Only the police, the secret police, the military, the hired servants of our rulers. Only the government -- and a few outlaws. I intend to be among the outlaws" - Edward Abbey