With the limited experience I have of treating sawn or even S4S stock to give a planed look I agree with Roger. Smaller, lighter, quicker strokes. In my case I wasn't trying to develop a perfectly flat and precise surface over the entire length of the timber - but one that was 'smooth' with makers marks evident. In no way similar to jointing a piece for furniture.

And like the bike and gears - moving the work to smaller gears and quicker revolutions of the pedals makes for efficient mountain pass climbing.