This is my very first post. I’m 47 and weighs roughly 80kg. I had both knees with torn ACL and had since repaired. Started squatting in January 2015. My starting max was 135lbs and i hit 315lbs in July 2015. But since then I have not been able to improve. I squat 4 - 5 times a week, changing from front squats, high bar back squats, low bar etc. I have done 10x10, 20 reps and most days i squatted to 90-95%. My next goal is 4 plates. Considering my age, is 4 plates too much to shoot at? Thank you.