The crux of the problem....... is L-both R-both good enough or is All-both needed? And if so does it run the risk of damaging the engine? Is that risk dependant on the exact prop engine exhaust installation?
It never ceases to amaze me how such basic procedures end up shrouded in mystery; with most of us doing "just by rote" what we were taught by people who were also "just by rote" doing what they were taught!