Good point MM. People seldom peak at the top or even stretch at the bottom of the movement. When loading too heavy you're most likely going to sacrifice form by not stretching at the bottom of the movement. Here are a few points to remember when calf training:

!. Use good Form (fully contract and stretch each rep)
2. You support double your bodyweight on each step and heavier when you're running so yes push the poundage but not at the expense of your FORM!
3. No two people respond to calf training the same. Some make great gains with lower reps and others grow from repping out. Use a full range of reps/sets, and movements. Standing calf raises, seated calf raises single leg calf raises, donkey calf raises, leg press calf raises....blah blah, you know. Do them all with good FORM. and Bless you all!