I too am a large man and can be intimidating even though I make no attempt to be unless my size would help defuse a tense situation. When shaking hands, I give a firm but not competively painful handshake and then stand my ground at arms length. The reason has noting to do with "personal space" for me, it's just easier to focus on someone who isn't 5 inches from my nose.
I do find however that when I am in en femme mode I do tend to have a much gentler handshake but still not a "finger-tipper" That bugs me in either mode.