We've done knock sensing for nearly 20 years and done a large number of Porsches but the factory has already placed the sensors well, with a sensor for each bank and an acoustic bridge between cylinders.
Key on any installation is placement and being able to filter out extraneous noise which can be mistaken for knock.
Not all OEMs use full on knock sensing at all times. That went very wrong for Subaru on US spec STis and they had a lot of engines to replace in 2008-2009MY because of an overly aggressive advance strategy and slow retard strategy. At WOT, all OEM ECUs I've ever evaluated through the OBDII immediately retard timing a bunch as soon as MAP goes past a certain point since you know you're going to knock there with 45 degrees of timing in and there must be a reasonable safety mechanism in place if a knock sensor fails. Open loop mapping is still important as a fall back.
We've never recommended to use knock as the primary timing tool, preferring to have realistic timing curves mapped and use knock sensing to modify those in case of bad fuel, wastegate failure etc. Performance, racing and aircraft applications are much different than OEM automotive though.
Most OEM ECUs for a number of years have used DSP to track which cylinder was just fired and a single or twin knock sensors to track which cylinder knocked. They can retard timing in that cylinder only or any which knock. Very sophisticated stuff running millions of lines of code and processors more powerful than many PCs.
I'll be running our Continental O-200 on the test stand next month and plan to do some tests with knock sensing on that to see how feasible it is with a single or twin sensors on a pushrod, air cooled, individual cylinder design. Will put some 87 octane mogas in it and see how far we can push it. With the EM-5 PC data logging we can observe knock activity and map the best strategy to deal with it. Should prove interesting. If we learn something new there, that will be incorporated in the next CPI and EM-5 software releases so we're ready for that "low octane" unleaded avgas.