Injecting my comments regarding TSIO-520 and my current io-550:  the movement of cowl relative to engine (therefore spinner) is dramatic.   In tests I did to resolve interference issues in a C414A and my Lancair Legacy I determined through witness marks, scuffing, dabs of TorqueSeal and spray paint I determined that the engine moves forward, down and counter to prop rotation.   In the front, it can be 1-2 inches forward, a circular twist of at least an inch at the rocker cover and a downward movement of an inch or more.  All this relative to the cowl and permitted by the flexing of the engine mounts and dependent upon horsepower and trq.  I can't recall Lorne's setup but his numbers do not appear unreasonable given my results.   Just spray some light white primer inside the cowl and you can see the extent of any movement after a flight relative to baffling.  If the cowl itself is deforming, that is another variable.