One thing that you should know Bruce is that Subie has a gear set for turbo and a gear set for non-turbo so if your running lots of HP sure you need the stronger gear set but I don't think you will need it. If you are running the box with SGear's reverse R&P then from the front of the car to the back you have the 6th or 5th gear in the nose cone so the oil flows to the back upon acceleration and SGears adds more oil to the tranny to make sure the 6th or 5th does not starve in acceleration and also due to the R&P spinning reverse which may or may not affect oiling pattern.
If you are using the tranny in the regular orientation, as it exists in a subie, I don't think there is an issue at all.
Re My ratios. As you quoted above the ratios I have make the car quite petty and you can nicely row through the gears. I would have liked a 3.91 but in your car with top down you won't hear the engine anyway Enjoy the unbelievable torque.