the holes on your predrilled replica bottom look to be about right.
The grips you have were probably made a bit long so you could trim where you needed. Even placing them like you have in the picture they're too long on both sides. Remember you have to account for the graflex band.
I'd suggest you assemble the saber and orient the bottom piece the way it should be, then lay the grips down so that the holes line up. then mark with a pencil where they need to be trimmed on both ends.
If you use an exacto knife and go slow, those things cut like butter and you can get a nice clean line.