[Icelander]

Realistically, of course, rowers can propel a given craft at Move 2-3 fairly easily, but going faster than that requires extremely specific design goals that include as much length as you can practically attain, radical streamlining in water and as little weight as possible.

Going from Move 2 to Move 3 and from Move 3 to even higher Move scores involves non-trivial diminishing returns in terms of efficiency. Getting the maximum possible rowing speed of Move 5 or so has always been an extremely expensive proposition that requires you to sacrifice most every other consideration for your vessel.

I doubt very much that it's realistic to allow adding just +50% to your number of rowers and the expence of a single additional system to go from a fairly typical galley speed of Move 4 to the highest we have evidence of, for Move 5.

It seems to have been a ground-up redesign that sacrificed nearly everything else for speed and required almost as many rowers as it was theoretically possible to cram in there.