Help needed to get the perfect crackling!

Spacegirlley

I need help, I'm hoping someone here might be able to give me some insights. I'm cooking for 16 people on the weekend and I will be making a roast. I'm going to be cooking two roasts, a 2.1kg and 1.2 kg pork roasts. So one will take about 2 hours the other about 1 hour and 15 mins. If I want to get crackling on both and have them finish at the same time, what would be the best way to do this?