Poor Smurf. I keep looking at the picture and hoping that some magical solution will pop into my head.

At first I was having a hard time wrapping my head around it because my bike is a smallar than yours and compact (XS/49 with a 51.5 cm virtual tt), and even though it's a bit tight, I can functionally fit two 24oz bottles on it -- they *do* have to be the new wide-mouth, screw top style that's a teeny bit shorter than the old "flip-top" style, but I can actually use them both while riding.

Click image for larger version.  Name: small scott image with new tires & saddle.jpg  Views: 229  Size: 68.9 KB  ID: 9101

But as Margo points out, the lower boss on my bike is below the derailleur mount. Grrr. Boo on Blue.

Have you thought about Arundel side loader cages? I have regular Arundel cages on the bike in the picture and I've been very happy -- they're very solid but also reasonably flexible. Not that light though.

Anyway, I hope you find something that works. I empathize!