I have a Bushmaster Varminter with a flatop receiver.  I have the scope mounted as far forward as possible and still need it moved forward about another inch to make the gun "fit" better.   When I bring a rifle to my shoulder I don't want to have to adjust my position to get a full view through the scope.  The gun itself seems to fit me, I just need the scope moved up, so I don't want to lengthen the stock.  Does anyone know of some type of rail extension for an AR?
TIA