I got to play with Fin Sushi over the weekend, I can confirm that it's INT+5 and Acc/RAcc+ 15%~ like normal sushi, but I don't know about any hidden stats(hHP/hMP+, Resist+, etc.). I thought it might be DEX+4 at first too, but then realized that was coming from my Goliard Clogs.
I'm pretty happy with it, would've been sweet to have STR+ on it too, but I won't complain. I got to toy around in Sky as RDM/DRK now that I can finally carry my full gear set around again(thank you, Gobbybag!), used Fin Sushi and melee'd vs. Genbu, my damage wasn't anything that'd show up on a parse, but my hit rate was surprisingly high, and when I used Souleater I did crank out a pretty good chunk w/ Joyeuse(I need a Haste build
)