The top tube on a frame I have is ever so slightly bent. The top tube is bent down in the center about 2-3mm. Its a very gradual bend. It looks as though someone might have landed on the toptube with all of their weight while riding(ouch, I hope that didnt happen for the previous owner's sake!) The rest of the frame seems straight. Is this slight bend going to greatly affect ride quality? Does this make the frame worthless? THANKS!!