I don't mind at all sharing what I did. It's not simple and required some imagination and some minor shop work.
I am able to move both the top and bottom masks up and down by remote control. I have up to 8 pre-set positions available, but only use about 6 right now. Different buttons on an X-10 remote are assigned to different aspect ratios and it will search these out in random order, so I can go from any one to any other one in any order.
Motors are physically modified DrapeBoss units. I took the drive wheel off, turned it around so the flat side is out, drilled several holes in it and mounted it to a roller. Thus I have programmable motors on both the top mask and the bottom. I used some 1 1/2" rollers from discarded specialty shades which aren't available, so you'd have to get an extremely straight 1 1/2" dowel to use. It has to span your screen width.
The case on the DrapeBoss has to be taken apart so that the motor portion faces the screen and the electronics half faces outward so you can program it. I made a wooden mount so this would work.
Shades would have a slat in them that you pull on to raise or lower them. I used an extremely straight aspen 1 x 4 for this purpose. It's very light weight and stay straight. You simply sew a rod pocket in your fabric that this can slip through.
Next problem: Counterweights. Obviously, the bottom shade has a roller on the bottom, so something must pull that mask upward. It won't float in mid-air Eyebolts are inserted in the end of the aspen 1 x4, go up to a pully, outward a little bit to another pully and a sandbag weight is tied on the end. This on each end provides the proper tension.
Problems: The DrapeBoss unit has a slip clucth that won't hold the weight of the masking system in place without help. It slips. To solve this, I decided to make the masks absolutely weight nuetral. On the bottom you simply make the sandbag weight just right so there is slight tension on the fabric, but no more. On the top one, I wrapped a cord around the roller and put a weight on it to counter balance the weight of the top mask so it is once again weight nuetral. When these weights and counter weights are perfect it never gets out of sync.
I used black velvet for my masks. Also made frames from 1 x 2 and covered them with velvet to hide all of the motors, pullys, etc on the sides, top and bottom. When you look at my screen you see nothing but white screen and pure black for about 18" all around. Makes an awesome picture.
Negatives: Even thought the DrapeBoss is rather cheap, especially for what it is, it still takes two. That's about $400. Also, you have to be somewhat handy with some tools, including drilling the aluminum drive pullys for screws, and building mounts for the DrapeBoss units. This is definetly a DIY project and each person would have to judge their skill and appetite for such a project.
I don't anticipate this description would be enough for someone to tackle the project, but I would be happy to answer any additional questions. I hope to eventually make some close-up photos that can be used to convey the techniques.
By the way, the DrapeBoss has to have the open and close limits programmed in as a first step. I simply used the open position for 4:3 and the closed for 2.35:1. Then the intermediate stops are used for 16:9, 1.66:1 non-anamorphic, etc. It works perfectly every time.