I appreciate the help. Got it installed now but waiting til a cold night to burn it.The rear clearance is 14", side clearance is 15". Coming off the flue collar with an elbow and then a long horizontal is a real draft killer.
Get rid of the key damper, you won't need it now and it restricts draft a bit even when open. Come off of the stove flue collar with a 45º elbow, a short straight section, and the another 45º elbow. If you can do this with double-wall stove pipe it will be much safer. I'd also remove the black curtain on the back wall and the red box on the floor.