Homemade seconary air controll for Oslo

Sometimes when it's really cold, say -5 C and colder, my Oslo can't be shut down to my satisfaction so I decided to try and build a secondary air control for those times when she's running a bit too hot even with the primary air fully closed. I have a 6" stainless liner 25' straight up and no option for a key damper because I only have 4" from the back of the stove to the T in a hearth mount installation.
So far it works very well, no down side that I can see and I think it's a better solution than a key damper: on those cold nights when I want to go to bed feeling secure and knowing there will be plenty hot coals in the morning, instead of having a firebox full of primary flames and a stove top temp of 650 or 700, I can now achieve a stove top temp of 500 with nice secondaries and a glowing firebox with occasional primary flames.
I used a piece of black stove pipe to make it, basic tools and very limited metal working skills. Here are some pics:

webby3650 said:

Have you checked all your gaskets real good? With a Tee and 25' I'm surprised your draw is that excessive.
Tons of research and engineering goes into these things, I'd hate to modify one, hope it works out ok for you.

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Thanks Webby; I have checked all the gaskets with the dollar bill test and smoke and they are perfect. It is a 10 yr old stove though so is it possible that air could enter elsewhere? I just thought, after reading John Gulland's article, that it would make sense to add more control for those really cold nights. It's easily removed and I didn't have to alter the stove, do you think it could cause a problem?

webby3650 said:

I don't see how it could cause any problems. I like that it is removable, guess I missed that part. I'm all for improving something if need be.
Keep us posted on how it works out!

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OK, I will, so far so good, but I've only had to use it a few times when it's been really cold and even then I close it half way at most and it does the trick.

Thanks for compliments, I've used the ball of foil and this is a bit more convenient and adjustable, it will definitely be good to have this coming week, it's going down to -12 C.
The article I read is "The Florida Bungalow syndrome" by John Gulland.

begreen said:

The term secondary air control seems to be a misnomer here. This appears to control the primary air (OAK) inlet, correct? If so, this is more like a master control. It seems like there may be an easier way to do this with the primary air control slider.

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I thought with the primary air fully closed this control I added would affect only the secondary air. Is there another intake somewhere else [other than the OAK]?

webby3650 said:

In this case it would be the secondary air. From what I understand, the primary air is shut down all the way and this contraption reduces the secondary air that is still being introduced. The primary and secondary air are pulled through the same hole in the back of the stove and then separated internally. This just adds some extra reduction in the secondary air that has no external control.

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This is how I understand it too.