Thanks in advance,
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But you will need to have a edgeblender processor if you want to do this on 4 projectors.
Maybe this image processor from projectiondesign can accommodate higher resolution than 2K, it does edge blending between several projectors AFAIK; http://www.projectiondesign.com/products/multi-image-processor
You should try the RGB Spectrum SuperView 4K.
It can take four projectors and create a single image, plus give you 4 additional 1080P windows, but this doesn't work well with projection, only with videowall wall display panels or with a 4K panel, like Planar's 84" 4K panel.. You need to use projectors that have edge-blending in the internal menu, or, use stand-alone edge blenders (1 per projector). The SuperView 4K has mullion compensation for the overlap areas.