Sorry Danmark. Your post is too conservative/pessimistic for this thread!
mr_g, can you get real detonation and record it?
If no, you can use my frequencies from wiki (c20XE - same engine)
Rob has some guidance. I use somewhere like 10...15% for noise maximum (100...150digits from 1024 full scale) and two additional rows in vems3.ini file for datalogging.
In any case i can see detonation in logs.
BTW dainiuxsky report knock system as non working in 1.1.62...68
Gints