HUH? how do you cut a log from the bottom up? I am a little city boy and don't know crap about cutting logs so what am I missing? I am thinking you would want to cut the roof first as it would be supported by the framing and not bind. Where as if you are cutting the floor, who cares if it binds some and the cut looks like crap.
I just recently cut up a Rambler parts car with the sawzall and it went pretty easy!