Someone posted a picture in another thread of DIY doubles made using a plastic cage (the kind with two separate loops for the strap to go through), nylon straps, and pedals with two strap holes per side - basically the straps were threaded in an x, one per loop in the cage. I haven't tried this, but I'm considering it since it's way, way cheaper than doubles and my cages are too small anyway. If you end up doing this, let me know how it works out.