Sliding seat for cruising rowboats

Sliding seats are a big problem for cruising boats, because they take up all the middle of the boat and get in the way when you want to for camp, cook or just laze around. Worse than a centreboard.
Rick Thompson in the San Francisco Bay area has built one of the most interesting rowing/sailing boat designs around, John Welsford's Walkabout. Now he has added an ingenious sliding seat mechanism that runs on the side flotation tanks, leaving the centre well free for other purposes, such as sleep. Rick describes it in the very excellent John Welsford forum thus:

I'm pretty happy with it so far. I know JW is not so keen on sliding seats, and I understand that it probably burns more energy and doesn't do anything to change the hull speed limit on this type of boat.

For me, it is a big help to be able to use leg muscles as well as arms and back. Next will be some type of hold-down so the seat can be used fixed as well.
It's really hot here in inland California now, hope others are having good
boating or building weather.
Rick

I have to say I rather agree with John Welsford about sliding seats on long-distance boats. When you are racing over relatively short distances, you need to transmit all the power you can possibly generate into the oars. It is a sprint, so it's anaerobic.
Over longer distances, it is physically impossible to row anaerobically - the power you can produce is limited by the amount of air you can pump through your lungs. And you can produce this power just as efficiently on a fixed thwart as a sliding seat.
If you use a fixed seat, you get the other advantages of better control over the oars in choppy conditions and a more robust and simpler setup. But with the sliding seat, Rick will be able to make a lot of money by challenging fixed seat Walkabout owners to a race to "that buoy and back". Go, Rick!