Spin Semiconductor

I'm trying to understand how the FV-1 allpass filter (RDA & WRAP) translates to an analog allpass filter and vice-versa.

For an analog allpass (first-order): 90-degree phase shift happens at fc = 1/(2piRC).

Does the RDA/WRAP coef (kap/-kap) relate to fc in the same way as it does with RDFX: fc = (fs*Kf)/2pi ?
And what about the chosen allpass buffer mem size - how does that relate?

Any light on this would be of great help!

No simple answer to this one, the best I can suggest is to google: digital all pass filter phase response
That will give a result page with some good links to papers and sites that can explain the digital allpass structure and response.