it wont work when the triangle pivots the top triangle linkage will want to go down and so will the shock with it so you will have a lot of slack just refin that a bit and you will have a nice frame
I know the geometry is not perfect, but I was thinking kinda like the floating shock system that the trek session 88 has. Where the whole shock moves down a little bit while still compressing at the same time. Your probably right that it would have a lot of slack, but it was really just a little thing I did for fun. And I just realized that the new cannondale moto frame has the same type of linkage and looks very similar but it only has a single pivot rear triangle...