If your shaft is too hard, that means you have an erection of 100%, not 60%.
By semi hard, are you talking about the angle of the erection? If that is the case, depending on what exercises you're doing, it could be just ligament expansion that is lowering your angle.
Me, after so many years of PE, it was along time ago that my penis stopped pointing straight out or up during an erection. Because of the suspensory ligament growth. If I squeeze my PC muscle during an erection yes it points straight out, but that is supported only by the blood pressure on the CC. Naturally, the suspensory ligaments is mostly what supports the erection angle.