I actually use about the same amount of fluff in my Herons that I do in my Spheroids. It's about 17 mm x 50-55mm. (.7" x 2-2.1"). Of course this will vary slightly with juice. But this setup has worked pretty much spot on for me.
If you go slightly larger and it doesn't release the juice, it's easy to push the top out and lift the tank. Trim the fluff some and reassemble without leaking all over. Then use a tool to go against the direction to spread it out.
If I remember you're using SnC wicks in your gear, so I assume a stiffer loop to get positive contact with the fluff. What's your opinion please with that fluff size using cotton/KGD, or would you recommed a different size?
I've been using 20mmX60mm as a starting place for the fluff in my Herons so far, picked up from suggestions noted elsewhere, and at that find the KDG works better if left a little larger and longer above the cotton cap to actually have it laying on the cap 1/4-1/3 of the way around it to make positive contact with the fluff. I'm not getting flooding, but sometimes I do get dry hits. Still not sure if it's the way I fluff/wick or my vaping style of long lung hits - maybe taking them too close together for the wick to reload? I just picked up on your comment that too large/much fluff may not release the juice. So with KGD less fluff? I have only been using 50/50 liquds so far, and sub ohm coils .7-.9. Want to stay with sub ohm coils in these two Herons for now as I have two more Herons coming from VA (maybe today/tomorrow) that I plan to do 1.2-1.8 coils in.
Wildvet is sending me a little SnC to try out, might even be in my mailbox already (thanks again). So thought I would try it in both a sub ohm and 1+ ohm coil, and without the cotton cap. That would give me 4 Herons all different to run against each other for comparisons - different coils, wicks, and with some suggestions fluff sizes.
Thanks.