External SPI Delay on ADAU1452

I'm looking to design 4 channel DSP with the ADAU1452. I want/need 400ms of Delay per channel, sampling at 96kHz. 

Can I use the internal delay for 1 channel and add an external SPI SRAM for the other 3 channels of delay?

I've seen comments to other questions in the forum that SigmaStudio only supports 1 instance of external delay, has there might be a software update to fix that?

and can I use an external delay that's 4Mb (512Kx8), or is it only designed to work with the microchip 23LC1024?