Well, what a disappointment (mostly). Here's what I found...
3 Subtank Nanos:
On one the chimney was about 2-3mm too short.
On the other 2, the chimney was about 1 mm too long so the tank would not screw down the whole way to seal the glass against the base seal.
3 Subtank Minis (these are all V2 with the airflow on 2 sides of the AFC):
On all 3 the chimney was too long by about 0.5 to 1mm so the tanks would not screw the whole way down to seal the glass against the base seal.
1 Toptank Mini:
It seems to fit fine. Chimney is the perfect length. Tank screws all the way down and chimney is long enough to seal around the top of coil head.
1 Protank 4:
No go. Chimney was too short by about 3+mm.
I didn't try any juice in any of these as I wasn't willing to risk losing juice (pet peeve in this post-9/9 era).
So chimney length varies from tank to tank.
None of this surprises me, really. As much as I love the subtanks, Kanger never was known for consistency in manufacturing with these tanks or their coils. Same for the Aerotanks/coils.
I have more subtanks and toptanks and PT4 tanks sealed in box but not willing to open them up to try.