I really do not think that it makes any difference in POI. I have not proven it, but you not only have the stiffness of the rail itself, but you have the stiffness of the scope that is mounted on it too. The scope being mounted above the rail acts as a brace to help keep it from flexing up and down, but there will still be a little. If you get an Ultra rail, which is longer, there is a screw that is comes down that you adjust. It is to be .010" off the barrel however, not against the barrel. I really do not think that the rail flexes that much (.010") and if it does, I would think it would effect the POI from shot to shot, bouncing off the barrel. I really do not think it does any good at all, I think it just makes you feel good that you have a screw out there. There has to be some flex, just pushing your finger against steel will have a little deformation, minute, but still there is some. The important thing is will the rail, scope come back to the exact same position each time it is flexed, I think it does. The flex has to be the same from shot to shot, again I think it does; as long as the rail is tight to the barrel and the rings are solidly mounted to the rail and to the scope.
