Lowering bust dart on Geneva

I am trying to make Geneva in size 18 with the D cup bust problem. My muslin shows I need to lower the bust dart about an inch. 67 year old boobs aren't very perky! Normally I'd box it and slide it down but I'm flummoxed by the big bump out which start pretty much at the sleeve seam intersection. I don't want to just change the angle of the dart because a downward pointing bust dart isn't attractive. Thank you for any help.