I make my bevels for the side planks using my rebate plane. I have drilled a hole in a bit of scrap Kahikatea and put it over the 'guide attachment'. It works very well. Once there is a resonable flat I sometimes use a bigger plane. I plane down to a pencil line which is the same width as the stringer behind.
Also planned king plank today. Away for 3 days now. Random Orbital sander on my shopping list soon.