In a nutshell, cajun tuning on a C box would have the Bs and the Es -15 cents and the Fs +15 cents (from equal tempered tuning). However, if you play a lot in F (or third position), the sharpened Fs would be a problem so you may want to keep them at 0, or anywhere in between for a compromise.
Then the amount of tremolo is another question. I like a couple cents difference between the two M reeds. Even as little as 1 or 2 cents seems to fatten up the tone.
Tuning the A flat turned out really fine om my Hohner 1040, as long as I play in the key of C. But as you can see on my second chart the A this time will be +4 cent, as I plan to play mostly in G, and I think it will work fine. I consider to make the F +15 as you wrote. It gives a nice slightly sharpened lowered 7th in G. (I now see I used the wrong term "minor 7th" in my first post).
As for the wetness, I plan to make it 5 cent by the middle C. I believe that these industrially produced Hohner reeds don't really sound so good tuned dry as for example the handmade Italian reeds do.
Thanks for your reply.
Yes I'll play Cajun music, but tuning a one-row accordion in just 3rds and 5ths (and sometimes high 4ths) is suitable for any kind of music IMO, as long as you don't play along with other 12TET tuned instruments. My question was specifically about the tuning of A and F.
I just checked Lepistö out, seems to be a great musician, thanks for the tip.