So i have a car that i have unwrapped. when i layout using only one UV tile it gives the correct scale for each UV shell in relation to each other ( the chequerboard pattern is the same size across all shells). The issue I am having is that when i layout across multiple UV tiles I get shells that are out of their relative proportion compared to other shells. I have attached a pic of my layout settings. some clarification or help on this issue would be greatly appreciated.