I have used small 6 to 8 inch search coils on trashy beach sites and recovered some pretty incredible finds that were just simply not detected by people using stock and larger size search coils.
On one site last year, I was able to "snipe" many older US silver coins and pieces of gold and silver jewelry on an eroded section of beach over several days.
The vast majority of the other hunters searching the eroded beach were using stock 10 inch search coils and I believe the larger stock coil was the major reason why I found so many good finds behind the other beach hunters. I tried using my 10 inch search coil on this beach and it was almost unusable, one big nulled threshold from all the ferrous trash scattered on the beach.
After switching back to a small search coil, the beach came alive with signals.
The competition that searched over the area kept walking because the good targets were being masked. When I saw other beach hunters coming towards me I stopped digging so as not to attract unwanted attention.
This photo shows some of the jewelry finds I was able to recover while slowly sniping the area.
My advise is to go small and find big!