Don, 

I took a look at the Poseidon Site.  I suspect Poseidon himself may end up with quite a number of these.  Sculling is all about geometry. The only savings here is the price of the sculls as the rig is using conventional oars anchored on the gunnels (and you still have to buy those oars). With the Poseidon you are only buying the sliding seat. For nearly the same price the RowWing includes the sliding seat plus the rigger (the Aluminum Pipe with oarlocks at the each end), and most importantly, the optimized geometry between the sliding seat, the rigger and the rower (yourself). Placement in the boat is also critical but CLC has worked that out for you. The mechanical advantages of sliding seat rowing derive from both full extension of the legs to power the oars but also from the increase in mechanical advantage, and greater sweep that is obtained by using longer oars (sculls) pivoting on a fulcrom (the oarlocks) outboard of the boat.  With the installation shown on the link you would not be able to use the full extension of the legs before running out of oar.  It is also likely that it would be difficult to keep such short oars buried beyond a few inches fore and aft of the static position that the gunnel oarlock was designed to support.  In contrast the RowWing by attaching the rigger and the sliding seat and the streachers (foot plates), ensures that everything is held in the  correct relationship to work properly.  Piantedosi was an Olympic rower and MIT engineer.  I would go with his device, or as I am doing, at least with his geometry.  A good pair of sculls will bring you great joy and with a little care, will last the rest of your life.  Get help on selecting them though.  I would strongly encourage discussing the purchase with Concept II to match the sculls to your experience and ability level. Technique is important to prevent injuries.  The Concept II site also has some excellent instructional materials on proper technique.  

Bob R.

   If you are up for a modest construction project, and dont want to spend $1000 on rig and oars, look at the sliding seat and rigger kit from Angus Rowboats.   https://angusrowboats.com/products/sliding-seat-rigger-hardware-kit-with-carbon-fibre-seat

This would be easily fitted to the Chester Yawl.  I fit one to my Dave Gentry Ruth wherry and it works great.  The outrigger is strong and because it spans both gunwales with a single beam, it does not put undue stress on the gunwales, so they dont need reinforcement.  

I also have a NE dory and while i dont think it's a  great boat for sliding seat, you could fit this rig to it also.

I also made the nine and a half foot spoon blade oars from Angus plans and they are gorgeous .  I used sitka spruce with red cedar stripes.   These will look a lot better with your wooden boat than a pair of black carbon things.  My total cost for oars, seat and rigger was probably about Three hundrd bucks.

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���Oops. Sorry trying to learn how to send a photo. Need to practice elsewhere. But while I'm here, keep working on that new boat in the shop it will only be a few more months before we will be back in the water.

   Thanx all for the advice. I looked at all of the resources and found them to be helpful. I even emailed Angus and he said he has sold a lot of his kits to CLC Annapolis Wherry owners but no NED owners. He offered to consult on the NED build. However, wifie said NO MORE projects. Buy the ready made and get done with it. So yesterday I orderd the Piantedosi along with the sculls from CLC for the Chester Yawl. They were very helpful and put together an additional kit for the NED so that with a couple of bolts I can use the Wing on either boat. I took advantage of their 10% gift card sale and the savings covered the shipping. Now all I have to do is complete the NED. Thanx again.