Thanks for your responses guys, it was very helpful.
I also got a very helpful email from The Mogul which I'll paste below in case other people might be interested, I found it helped a lot with my questions.
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I've had a shooting guard with atrocious inside shot for many seasons, and he is able to "drive to the hoop for a layup" and convert. His ability to do this seems very similar to players I've used at SG with respectable inside shot.
One difference I've noticed is guys with respectable inside shot, while playing SG, will occassionally attempt all the other types of inside shots. Hook shots, alley-oop plays, everything in the book. However, they seem to do this extremely rarely (even while playing look inside).
It would take a very long time to train inside shot on your SG all the way from atrocious to even mediocre or average. I think that the benefit isn't worth the effort, and that your SG can still be very effective while running look inside.
I would have posted this on the forums, but I believe that you asked your question in the wrong forum (it should go in help), and I don't want my post to be lost if the thread is moved.
I hope that helps,
~TM