Gonna whack in new burner but fretting a bit about stuff. As photo, All new surround and hearth going in so not worried about that but flue is my concern.
Currently we have a Boatman coming up through a welded four inch and the new (unknown make but far larger stove) is a five inch flue.
Advice needed . . . . . . Mainly on the draught issues
Option 1; I run the wanted single skin 5" new cos i like the brass inspection up for the first 500mm then reduce to the 4" existing then up and out the existing collar.
Option 2; I run the same single for 500mm then replace the rest in double skin up through a new collar but same, bigger hole and replace collar
Option 3; i run a whole new thing straight up through new hole in roof
initial thoughts please