I was coming back to the forum today to ask the same question and while doing a search, I found your post.  I built a Mill Creek 16.5 last spring with the intentions of rowing it.  I was going to buy the drop-in seat from CLC, but then wondered about building one.  GlenL Boats has plans for one that look pretty good.  They even sell a hardware kit. 

https://www.boatdesigns.com/products.asp?dept=188

I'm just not sure about the oar locks.  I'll probably still buy the Super Comp Lites and want to be sure I have the correct oar locks.

I've got a CLC Oxford. While I was building it, I looked around for an alternative to the very expensive Piantedosi unit. The only plans I could find were the Glen-L. I scoured the 'net for opinions of this unit and every single one of the few I found were negative. All of them said the unit flexed horribly and some said they wished they had bought a commercial drop in unit. This was enough to make me break out the credit card and spring for the Piantedosi. Expensive and worth every cent.

Considering that the Glen-L plans and parts cost more than $200 plus the price of the wood and seem to produce an inferior unit, I think you'll end up regretting not going with a sure thing.

I was doing some figuring in my head and began to wonder if saving a few hundred was worth it.  I now have my answer, thanks.  Looks like I'll be rowing with the Piantedosi.  I already decided on the Super Comp Lites.  I hope the OP sees this.

I was close to building the Oxford.  What kind of water do you row on?  I was close to building the Oxford but our lake can get windy and choppy, so I decided to go with the MC16.5.  The other boat I considered was the wherry.  For speed, it would have probably been better than the MC.

I have been rowing a MC 16.5 with Piantedosi rig and super comp lites for three years and have been very happy with it.  The main drawback in chop is it tends to slap the bottom forward.  You would not have that with the Wherry.  Even with that, it certainly can handle anything I want to row in up to where I am catching crabs in the chop.  My boat weighs 65 lbs w/o the rig in and that is as much as I want to load on the car top by myself.  So, I plan to row this boat for a few more years and then replace it with the lighter Oxford.  I am in my 60s and these things get heavier every year.  If there are any other questions about this set up I would be happy to respond.

Paul

What kind of water do you row on?

 I'm very lucky to live near a nice flat river that is only used by rowing crews. I've taken the Oxford on choppy lakes and didn't like it. CLC says the Ox is good for up to a foot of chop and they are correct.

I primarily row on a small lake.  In early morning it is like a mirror.  I row with 4 folks who are all rowing single skulls so flat water is the target always.  We are in the S. Calif desert so we can row about 9 mos a year.  Have to knock off in summer as it is to hot, even at sunrise.

Paul

I admire the fact that Glen-L actually did something about the cost of sliding seat rigs by drawing up one you can build yourself.  The Glen-L rig is basically an Alden Oarmaster 1 rendered in wood.  It retains all of the Alden's problems (excess flexibility) and adds more of its own (considerable weight).

We spent a good bit of time and money last year developing a build-your-own sliding seat kit.  It was a failure, and we never brought it out.  Although you had to do a good bit of assembly, it cost more than the stock unit in the end!  That's no savings...  And it was still too flexible.  When I was about 15 years old I devised homebuilt riggers for a shell I had built, using plywood, thin-walled aluminum tubes from a junked TV antenna, and furniture casters. In some respects it was better than what I came up with last year.

Since Piantedosi sorted out their manufacturing and distribution issues in 2009, progress on our build-your-own rigger kit has languished.  If your time is worth a dime, it's a better deal.

A sliding seat oarsman generates so much torque and horsepower that wood just isn't strong enough for cantilevered outriggers.  If the riggers flex, you waste a lot of energy.  Aluminum (or autoclaved carbon) is what's needed, and homebuilt riggers have a tendency to either be too heavy, or to look like they were designed by a plumber.  The Piantedosi unit is sleek, stiff, and light.

I actually told my wife today that the rowing unit was back on the front burner and building one was off.  My 50th b'day is 15 Jan, so I may just give myself a gift!  We were up at our lake house in the mountains today and the water has that slushy ice on the surface.  The landing on our dock still had 5" of snow on it.  I'll probably build something lighter myself in a year or so since the MC is a bit heavy for lifting onto a Tahoe.

I built a sliding seat from the plans and hardware from Glen-L for my Bolger Dovekie, specifically for a coastal oar-and-sail race.  The hardware was not up to the task of sustained rowing; the rollers shed material constantly despite best efforts at lubrication. The rowing area was coated with a mixture of black powder and lubricant which stained all clothing.  In my next raid boat, I designed it around Concept II equipment which has been flawless.  After my disappointment with the Glen-L hardware, I contacted the company--not to complain, but to give them the feedback they need to improve their plans and products--and was stunned by the response:  "you must have been using it in a way that's not intended".  No curiosity whatsoever about mode of failure, etc.  Perhaps the Glen-L kit might be sufficient for occasional minimal use, but gee--what's the point then?  If you are really going to row your boat, follow the other respondents' advice and get a real rowing product.

Addendum:  John, I just realized that you put the previous post in on this topic.  You met my wife and I in the aforementioned Doviekie at the end of the Shipyard Raid at Port Townsend 5 summers ago.  I want to congratulate you again on the work you have done with CLC and your efforts to maintain top-notch plans and kits---such a contrast to Glen-L.

I wanted to thank everyone for their responses and good information.  It sounds like I really need to break out the credit card and buy a commercial drop in rowing seat. Thanks a bunch for saving me the money and time to build a Glen L seat.  Marty