I would imagine that you have tried different patch thicknesses and ball diameters, to see if that changes the point of impact. A first step would be to start filing the front sight down. If you have had an oportunity to handle a few originals, you would notice that the front sight is set rather low to the barrel, often it is nothing more then a nub. In the event that the removal is not enough, then you can consider either a rear sight or a bend as you say on the tube. I experienced a problem simular to yours on one of my Tulle's and added a rear sight. Although it would eliminate me from most smoothbore competition, it works out very well when used in the woods. I hate to refer to adjusting a barrel as bending and prefer to call it flexing. This is a drastic measure and generally should be avoided if at all possible, so I will not touch on this process. As mentioned earlier, the gun may simply not fit you as there may not be enough drop in the comb to suit you. If the stock was pre-carved and had come out of a jig then the drop is the same on them all. The only way to avoid this is to have a gun made to fit you.