There is a sticky thread that contains a calculator for determining your riser height, but it can also be used to determine how high you need to mount your screen so the people in the back row have an unobstructed view. The main link in the sticky doesn't work, but try this:
Do you already have a riser built for your back row? If so, you kind of need to work backwards through the calculator, plugging in trial and error screen heights (distance from floor to bottom of screen) until it spits out your current riser height. This will give you measurement "D" in your sketch.
Once you have selected a screen size and determined measurement "D", your top of screen height is a given, so ignore B & C in your drawing. If you plan on using the JVC's motorized zoom and lens memory features to move between aspect ratios, you will need to mount the projector's lens so that it falls within the screen area (not above as you currently show in your elevation). So A1 will need to be long enough so the lens is at least level with or slightly below the top of the screen.
Once that is all done, give it a quick check to make sure your eyeballs in the front row fall somewhere in the bottom 1/3 of the screen and the viewing angle to the top edge of the screen does not exceed 15 degrees.
A few questions:
1. Will your speakers be to the sides and above/below the screen or are you looking for an acoustically transparent screen that will allow you to hide all of your speakers behind the screen?
2. What percentage of your overall viewing will be movies? This should point you in the right direction regarding 16:9 vs. 2.35:1.
3. What made you decide on ceiling mount vs. fixed frame on the wall?