A zooming lens for BenQ W1070 Projector

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I have a BenQ W1070 video projector, and I am trying to magnify the screen to a larger size than what I have. The screen is currently 134 inches diagonally at a throw distance of 11 feet 9 inches. I've set the manual zoom to its highest, so that's as good as it will do.

The goal is to get a screen that's about 177 inches diagonally, if not another 20-40 more, if I have to stretch this for any reason. However, I'm stuck with the distance of 11 feet 9 inches. That's as far back as it can go while staying in the center of the wall. If I could put it in the corner, I would have about 17 feet, and that would be enough, but the projector doesn't have any kind of horizontal keystone correction that could make up the difference.

So I'm looking for something to magnify the lens itself so that the image will appear larger on the wall without the projector having to be crooked in the corner. I've researched this myself, but I wasn't finding a lot on replacing the lens for the BenQ. The results kept coming up about replacing the lamp, and ignoring my question. I did run into someone saying something about using a GOBO lens to magnify projector screens, but I don't know a lot about that. So my question is if anyone can think of any way to do this by either replacing the lens to one that throws a larger picture from a shorter distance than what I listed, or using something to magnify the picture the lens I already have is throwing. This projector is very clear and runs in HD, so I can risk degrading the image quality a little bit, and I'm willing to spend quite a bit on this, so pricing on whatever I need will be alright.

Thank you for helping me out. I'll continue looking into this myself, but I've found the users on this website to be the most reliable on any forum I've seen or been on.

[cyr]

Could you use a mirror to extend the effective throw distance (project at the back wall or ceiling and bounce the image towards the screen) ?

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Well, that certainly sounds like an interesting technique, but how big of a mirror would I possibly need, or how small of one. If you could go into greater detail of how this would work, or exactly what the effects would be, then, sure I think this could be something that I could do, or at least try.

I've continued looking into this myself, with not a lot of luck, I'm not sure exactly what to do with the lens itself, so I might need to use something like a mirror trick or something else to basically "fake" the bigger screen effect.