No, its not possible to get any additional memory working on the Efika board!

Using the GFX memory as system memory is very slow. It would only be useful as slow ram disk or as cache for gfx data. Second would only make sense when dealing with a 256MB card, as the second 128 MB are currently unused.

Reducing the GFX memory from 128 MB to 64 MB makes no sense, as those memory will reach its limit quite fast and then the system gets slow and more system memory is used.