It's been tested before, repeatedly, but links to specific tests, even my own, escape me at the moment.
Anyway, the maximum effect feedback cascade can have is 90%; you never completely interrupt an SCB charge.
An 8A SCB charge requires something in the ballpark of five c1 feedback rail hits or three c2 rail hits to reach near maximum effect. Im less sure of an A5, but two c2 or three c1 hits should do it.