The starter collar/duct can be found at any hardware store (Home Depot, lowes, etc...) I used 8", but it comes in different sizes 2, 4, 6, 8, 10" etc...you can also get black too.
YOu can just use a little piece of sheet metal to make a cover plate with tabs into the vent hole and just bend to fit.
Greg - no stiffeners on the outer shell, just a few on the inside of the firebox, there is about 2" in the front and around 4-5" in the rear of the stove, the fire box actually slopes down towards the back. If you look closely at the pics (Vent #3), you can see the discoloration on the side of the stove which indicates the firebox separation from the air flow around it. I also took a flashlight and looked in the top vent from the front to make sure nothing was obstructing my hole before cutting.
I will experiment with different air deflecting schemes.....!!
I may have to put an inline fan to help boost the airflow upstairs as shown in attachment.
So far so good!!