Muzz has a great photo of what I have found to be a "general rule" for "proper" scope placement. The ocular end (the one you look through) is placed (forward/back) so that it is aligned with the center of the pistol grip with an ever so slight favor to the rear if in any direction. And of course, this placement is determined with the scope on its highest power (if a variable) as that is the least amount the eye relief will be.
But as Thomae pointed out, cutting the stock would be my LAST resort, assuming of course the distance from the trigger to the butt is not longer than your fore arm.
Good luck!