thats a great hull thats for sure!!.
but you just ruined everything with your polishing and rounding it dude!!
round curves and soft lines are like the WORST thing you can do that a boat, causes major drag
i'd get that file out and sharpen everything or you will have a sad running boat.
as for being "too steep" i don't know what thats about. the best rudders are wedge rudders. a knife blade rudder isnt even as good. and i have run a knife blade rudder, I made it out of a Hankel's fillet knife, i used that and then replaced it with the exact Fullers mini rudder you have and its made a WORLD of difference
and leave the turn fin like that dude, you only round it, if its on a mono becuse when the water hits it the boat is on a angle so it doesn't give so much suction.

that grapuner hull ( got it drom DR jet ?) is a great boat.