Hi Chefsteps, I have an 8kg Top Sirloin Roast as well as a 1.2kg Top Sirloin Roast. I'm planning on cooking the 1.2kg roast first using Joule, and I’m aiming for a Medium Rare finish for both roasts. Your time and temperature guide says Six hours for the roast I want to do. However, the instructions do not account for a difference in weight and time. Do you have a means to calculate the difference between the 1.2kg and 8kg or is it six hours no matter the size?