The plate raise uses physics to make the exercise more difficult. A longer arm (or lever) makes lighter weights feel heavier because the weight will be farther from the working muscle at the top of the movement. With this in mind, you won’t need to go very heavy to accomplish the results you’re looking for. Most of the time, 10 to 25 pounds should get the job done. Try adding more reps to the movement first and then slowly increase the load.