Howdy CC,
You won't have to worry about "iffy" tides this week!
Today, Memorial Day we have a huge minus tide (-3.15 at 1312hrs)
Penn Cove is a famous shellfish area with several commercial oyster racks but the clamming is pretty solid as well.
I would wait until I had a 3-footer or less but my favorite scenerio is beginning a dig on a falling tide.
Often you'll find a strip on the beach that is very productive. Once you find the clam "hotspot", move laterally down the beach and soon you'll have a limit!
Hey! When is dinner???