I actually do have the same understandig of grips as Power Game.
To my knowledge the semi-western forehand is the exact same grip as the western back-hand or extreme eastern backhand.
These are actually the grips I use most of the time except I tend yo go more towards the eastern forehand when trying to go flatter on my forehand and more towards western on mid-court approaches.
What I find intriguing is that I can not keep the same grip going from one side to another. Altough the position shoud be the same they have some mino differences I can't tell.