Please help clear up my Throw Ratio confusion. I`m trying to decide on replacement for the Sony PJ thatI dropped. I thought I understood the logistics of how to work the size of the screen along with the Throw ratio. Having a Grandview motorised screen already,67" x38"with a diagonal of 77",,"I`ve tried a couple of online calculators giving the screen sizes to work out the required throw for preferred Pjs (H78+Sim 30h) only to find putting in the diagonal or the width of screen gives a throw ratio and changes the height and diagonal etc. Ihope i`m making myself clear. In other words my size of screen isn`t matched with the size of picture the calculator gives for the Throw ratio. Is this right or am I missing something .I wouldn`t want to have to buy another screen .Anyone throw some light on my confusion.