I have 6 to 1 40mm Ronstan blocks from my old A class on my 15yo daughters Mozzy and no way would you run a full 8mm line through them easily. I found an orange 8mm line that was more like 7mm that runs beautifully through them, if you go into a marine store and look at 10 mm or 12 mm sheet I'm sure you will start laughing, you can tie a 100 ft yacht to the dock with it