bottom blade bends

When my cylinder mower is set on lowest cut the bottom blade rests on the grass and the upward pressure from this grass bends the blade slightly. If I have a close setting between bottom blade and rotary cylinder the bent blade rubs on the cylinder. If I increase the clearance between the blades to stop this rubbing the cut is not as good. My mower is an inexpensive one: Qualcast Concorde 35. Although I could buy a better machine my question relates to this machine. How can I overcome the bending blade problem? The bottom blade is attached to the rigid framework at each end and bends upwards, mostly at the centre of its length. Clearance between the top surface of the lower blade and the rotor is minimal right across the blade width. I think a new bottom blade would also bend because the weakness is in the design. Any comments or suggestions please?

The remaining problem is that the degree of bending depends on the length of the grass and hence on the upward pressure on the lower blade. So there would be no ideal solution, only some degree of improvement. Incidentally the reason why the grass pushes up against the blade is that the front wheels are only about 1.5 inches wide and they push the grass right down to the ground because of the weight of the mower, thereby allowing the bottom blade to rest on the grass flattened by the mower's weight. Surely someone has a comment to make?