Bit coal in a new VigII stove,

That's good to know on the flu size, I do have 8" from the ceiling up but from the stove to the ceiling I have 10' of 6" and have wondered since I've read that others have been using 8" from the colar of the stove up. I going to get another foot of tripe wall to make the chimney taller and I think I'll get an adapter to go from the stove to 8" and then all the way up to the support box. Should I put an MPD in also?

Opinions vary on this but I prefer not to use MPD when burning bituminous coal because they can catch lots of soot and plug up the flue.

It doesn't seem like you have excessive draft anyway because you're able to get a 15 hour burn while keeping the stove at 400

Big coal, big smoke pipe = nice fire.