On the topic of flattening only one side of a log for a joist or rafter for the purpose of producing a nailing surface... I have seen it many times. I should mention however that in examples I've seen it's always been a fairly small flat surface. I believe that if you remove too much from one side of a log then you have too do the same on the opposite side. This having to do with tension/stress within the log. Also, I've read this in one of Jack Sobon's books.
There are many ways to skin a cat but in the end we all cook with water.(whatever that means)
Thane
