BillV,
Tom and I both think that Pine Valley was a great influence on Flynn, and maybe Flynn had an influence on Pine Valley as well (circa 1921). The Pine Valley influence can be seen in Flynn's use of interrupted fairways and undulating sandy waste areas. He used these effectively at Atlantic City CC (1923), Denver CC plans (1923), Opa Locka (1926), Boca Raton North and South (1929) and closer to home at Merion East in the quarry on 16. When Merion East first opened for play, the quarry fronting 16 green was mown rough. For a time it was fully sanded. It was probably sometime before the 1924 Amateur that the quarry was turned into its present state with less formal bunkering, Scots Broom, and sea grasses.
Flynn used triangulation a lot. It is readily seen at Kittansett, Shinnecock Hills, Boca Raton South, Brinton Lake Club (Concord), Eagles Mere, Huntingdon Valley, Indian Creek, Pocantico Hills, Mill Road Farm, and others. Windy sites, especially by the sea had several areas where triangulation was used.