Don't be a fool, Jed. Use two lanyards when cutting with a chainsaw.
Sure, there's over the top safety mavens a'plenty who will sing the praises of top rope safeties, and much more besides.
But please hear this old, old climber, descended from your own PNW genetic tree climber base: don't get stuck in the oldest of old school paradigms, where we were taught to think anything beyond a flipline and a good pair of spurs was a stupid waste of time.
That way of looking at climber safety comes from the many decades gone now perception that a logger's life was not worth much...certainly not worth enough to take any effort at protecting. Save a few minutes?? Sure, and if every now and then that uneducated, has to work under whatever situation the bossman says he must, hard working man dies...too bad for him and his family, but by the gods, the company made some money still.
I beg to differ.
Go with two lanyards, or a lanyard and a top rope (hate that latter choice myself unless I have to go up to the top for some other reason beyond just the rope placement...whatever
). But by hook or crook, keep yourself safe.