Can you link the videos? A quick look at youtube didn't bring up anything good on the V3..
That's going into an 8" ID chimney? In that case, draft should be decreased some.
Are you cutting the air fairly aggressively? Once you are seeing the beginnings of secondary burn, cut the air in increments. You want to keep the secondary going, but eventually have the air low, where there's just lazy flame coming off the wood but the secondary is burning strong. You need dry wood for this to work well, though.
Now, I don't know how this stove is designed to burn. Can you cut the air to where the load is smoldering, but the cat is still eating the smoke and you have no smoke out the stack? Or is it pretty much a secondary-burn stove with the cat just there to clean up the burn a bit more?
Is the cat well-protected, or is it pretty easy for the flames of a high fire to hit the cat? There doesn't appear to be a bypass..