Hmmm... It would seem like it should be a pretty easy mod, although 1cm of unsupported cage would be quite tall.

Which pedals screw the cages on vs pedals that peen the cages on?

Any chance you would have access to a shop that could anneal the aluminum, then heat treat it?

Are you also using toe clips?

Do you know if your femur or tibia is short, or both? It might make a difference on how it pedals.