I have just stripped down my printer and sort of see what you mean. I have also opened up the bottom case to have a look inside and replace a noisy fan. When removing the two 8mm steel rods (362mm long), they are both bent, and when removing them from the holders at each end, they are immediately forced down as if being held at a wrong angle under pressure. I intend to replace the rods tomorrow but have two options to solve the out-of-alignment holders. I can either unscrew the holders and add some plastic washers to allow enough flex, or I could use the old bent rods to prize up, and hopefully not break, the clamps so that there is no downward or wayward pressure on the new rods. I prefer washers. It would be interesting to know what tolerance the bed is supposed to allow. Obviously the flatter the better. I would have expected 0.1 and below. Mine is all over the place and need to replace both the heated bed and the heated bed supporting plate, which is flimsy enough to be bent out of shape by the spring loaded thumb screws. I have bought a 4mm thick piece of aluminium and it does not bend if I stand on it, but it did not arrive flat! I think the next step is either a garage head skimming machine or a new bed support from a service like at tehnologika.net. I have emailed them to see if they will design one if i supply measurements. I tried glass, but that was being bent into a dome by the clamping to an already bent heated bed.