I saw this item and placed a token bid of $77 which I really didn't expect to pay.  It held up until the happy hour sniping an sold for $156.

I have always believed that Cox engines would have been better with a lot intake and less exhaust, like modern OS's.

Maybe the new Cox maker in Canada will take note of this and offer such cylinders to the aftermarket.

No I have never gotten a hold on one.  As with all things engines, you need to get a hold of one and try it yourself.

The Babe Bee had one intake.  The 2-port TD sleeve increased performance to the point that in my neighborhood, which had a lot of 1/2A flyers, every Babe Bee and Golden Bee was upgraded to a Super Bee or Black Widow within three weeks of discovery of the 2-port TD sleeve.

Compared to every other engine I have ever seen, the standard Cox sleeve has way too much exhaust and not near enough intake. 

I have a hunch that the 3-intake/1-exhaust sleeve will increase power to the point the bottom end won't take it.  Maybe that's why Cox intentionally degraded the top end.  But I have good supply of bottom ends, so I could afford a few failures if the sleeves ever hit the market.

Actually, the most powerful TeeDee .049 cylinder is the one used on the Venom. One extra flute on each main flute opposed to create a swirl flow in the incoming gasses.

🤠

Your theory is consistent with the reality of modern 3/1 engines vs the equal-ported engines of the past. Engines of today, such as the OS FP & LA Series use substantially less fuel than equal-ported engines of the past. 

Of course the mouse racer in your example could have won the race by adding less fuel to its tank.