Correct me if I'm wrong, but can't you wear a tinker talisman once you're at 30.1 and it won't add damage?
I used my human guy with tails and it did not seem to increase damage at all. So then i started to think about carp.
So I went back and made a gargoyle character. Put 10.0 carp (this gives 50% chance)
and 30.0 tink (and a 27 tink talisman) made boxes quickly ,
I found great variability between crates but I think this combo gives the minimum damage
Good find onlyindreams!