re: Planking

I used to build the whole thing in my head over and over as I built. 
Yeah,  Sketchup would not be much help out on deck...

Question on the planking.  As each plank is tapered at the ends, do you taper both edges, or just one?

And also how do you determine how much to taper each piece from the get go?  
I'm going to guess (just to see how far off I am) After you mount the first few bottom pieces and the top piece or two,  you measure the distance to cover and divide it by the number of pieces you are going to use? 

Figuring out how to do something you have never done is what makes a good challenge.