Don't go to that much trouble. I can visualize what you're describing. I thought you meant you built something like a keen vent, but I now understand that you built and automatic damper. That's slick.
Our ducts are the old rectangular type. Sounds like you have the same. Cool idea. I assume you have some logic that prevents over-pressure in the system?
I have an in duct blower sitting in my basement for almost a year now waiting to be installed. My neighbour is an hvac guy and got it for me to install. My office is too warm in the summer because of the computers so the blower will get more cold air to it. The rest of the house is perfectly fine.
In winter all is good though. I guess I have a bit of a push to do that project in the spring.
Myself. It was a PITA. And I did it twice. The first fan I bought (cheap-ass Suncourt) burned out within a few months. The second one I bought (Tjernlund M-10) was expensive, but has lasted since Sept 2015. No issues at all.
This isn't fair. I am a two finger typist and a sloppy mind. It takes me too long to add my two or three sentence reply to things. You guys need to slow down and wait until I am caught up. 
The dampers don't change how much air is pushed, just which direction it goes.
I'm on my laptop at the moment. But it's not a race. However, I_will_go_S_L_O_W_for_you.
Well....I'm sure the second time was easier, right?
I'm sorry...I'm really trying hard not to laugh at your pain but this is exactly the type of situation I get myself into way too often.
Yes, I understand. My knowledge of Keen (minimal) is that they have built-in logic that will prevent too many from being closed at once, because doing so could create a back-pressure on the system and cause pre-mature failure of the blower. But I get the difference between dampers redirecting the air and a vent closing it off. So maybe I'll just withdraw that question because it's sounding dumber the more I type 
Actually - no. I had used the Suncourt because it was light. The duct runs vertically, and I had no easy way to build a wooden frame to support the in-duct blower. The second time around, I had to work laying upside down in a space that's about 2x2x2 - building a frame to support the heavier blower.
I am 4 years older. If this burns out - I'm hiring someone!
@aaiyar I wish you would post your heating/cooling rules. I think may could benefit from your extensive look at the whole process.
I have taken several ideas from what you have.
Will do. Not today - unfortunately I have to do laundry.
After all the messes I've gotten myself into, I hope I would be smart enough to hire someone the first time at this point. But knowing me, I probably wouldn't. 
We are all 4 years older than we were 4 years ago. I don't get the significance? 
I don't get the significance either. Unfortunately, my back does. 
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