Yes a 27 offset would work with 9.5 inch wide rear wheels. It would be equivalent to a 39 offset with 10.5 inch wide wheels. That offset is aggressive, but would work if the car was slammed (because the wheels will camber inward.) For example, luigimaster24 was running a 40 rear offset on his 10.5 inch wide Forged1 wheels and he believes that offset was perfect.
For a 9 inch wide front wheel there are varying opinions on the perfect offset. I believe 25 is the most aggressive with no rubbing. I'm going to do a bit of research on this though and let you know.