On the subject of cold-hardy CNBG... We stocked 600 3-5" from the same supplier 4-1/2 years ago that esshup obtained his fish from.
They have done extremely well 30 miles east of me. Impoundment is a community pond I assisted with the build and seal, with a max depth of 12' and very little flow-through, has a low acreage water shed and the fall of 22 we stocked 70 SAE to help control the numbers as we have SMB as a main predator and we all know they won't control BG reproduction.
All year classes were/are well represented with numerous fish from 4-9" and scads of 1-3".
It's been in a very harsh region and I have to say I am surprised at the survival.