I also made a spreadsheet for the stacking % and the possible outcome:
http://forums.d2jsp.org/topic.php?t=71891386&f=74It is assumed that there's an even distribution across the fish quality
I also made a spreadsheet where you can enter your cooking / fish rank and you'll get the outcome of how much fish you can stack of each tier (an automated lookup of the second link that uknumba1 posted)
Not sure if I'm allowed to post that, but feel free to toss me a pm if you're interested
from my experience:
Try using rods that match your rank, you can use higher ones but you'll reel in the fish much slower
Certainly cook along with fishing, just be aware that this gets problematic at higher ranks: When you only get prof from t3 fish and you're fishing t1, t2 and t3 fish, only a third of them will give you prof. That ends up in your fishing outleveling the cooking by far