Pipe Size 6" vs. 5"?

Our block chimney had a 4" pipe from an old gas furnance, that I removed and enlarged to 5", I didn't want to take any more of the bricks out than I had to for structual reasons (100+ years old). The chimney is in the center of the house and goes thru the peak of the roof, probably 30' high or more.

I put a 6" to 5" adapter on the stove and ran 5" to the chimney. It is only about 5' of pipe and 2 elbows. Anyone see any problems with this setup.? Or should I have put 6" to the chimney and adapt down? I have no Baro damper yet, my dealer said I didn't need one.

It draws Really, really well and seems to be working fine. I have a CO detector mounted right above it next to where it hooks into chimney and hasn't gone off. I opened the door briefly and the CO went off, but opening the ash door, the CO doesn't go off.

I have a Draft gauge coming and temperature sensors, but its been running for 3 days and seems to be burning well. The pipe temp is around 100-120 degrees. Once I know the draft, I will add a baro.

With a 30' interior chimney you shouldn't have trouble with a 5" pipe.
You do need a barometric damper, now more than ever.

I would look into a cast in place liner, it would strengthen, seal and add years of life to the old chimney.