Like ryanmac, I registered here just to post this, both to show my appreciation for this forum (and especially this thread) and share my experience.
TLDR: upper smoke deflector was too restrictive
We had an F2450M installed early Nov 2022 on the main floor of our bungalow. Chimney goes 4 feet straight up from the stove, 2 x 45* bends backward, then straight up through the ceiling, attic, low-pitch roof and outside. Total chimney height is ~12 feet.
After lighting our first fire, smoke began pouring out of the open door. Closing the door just choked the fire out, even with damper full open (which makes sense as nothing was really hot yet). Wood was all <18% moisture and kindling was <5%.
I assumed it had to do with the column of cool/dense air in the chimney, so I preheated with a torch and restarted the fire, leaving the door open so the fire would really catch. It filled the living room with smoke but eventually the fire pulled enough draft to stop trickling from the damper control and be controlled by the damper. Chimney thermometer read ~250*F and climbing.
However EVERY time I opened the door to add a log, smoke would pour out. It didn't matter if I opened the door quickly, slowly, hot fire, or after it had died down; the end result was always a smoky living room. I grew up with wood stoves and have recent experience with Napoleon and Drolet units, so I figured Regency wouldn't design something to perform like this. Obviously something was wrong.
Thankfully I found this forum. As was suggested here, the installer had left the rear 4" blanking plate in the pedestal (not Regency's fault). I removed it but nothing changed. So after it cooled, I pulled the top metal deflector and relit. What an absolute difference! Smoke all went where it was supposed to, regardless of door position. I couldn't believe how restrictive the deflector was, but I was so happy to have it working properly.
I figure Regency put the deflector there for a reason, so I bent it up a bit so it would be less restrictive. I reinstalled it for my next fire and the stove performed just was well, so I've left it in there and everything has been great since.
Sorry for the long post and bringing back an old thread, but this information is still very valid today (ours was built Oct 2022). I guess Regency hasn't remedied the angle of their deflector, but without this thread I don't know if I ever would have thought to check the deflector. So thank you to everyone here for your help, and to ryanmac for sharing your experience.