Well I think I am gonna abandon trying to get the V9958 to work with SRAM.  

Latest testing was producing the occasional write failure -- its probably a bit beyond my skills to fully understand..  I suspect i need to do a bit more latching of the address lines - but doing this increases the chip count - so to keep moving forward I have changed the design to a more conventional DRAM model.

I can only fit 128k VRAM on the board's dimensions - but thats more than enough.

New PCBs have been ordered - so just have to wait until they arrive.