RE:Saturday Cape Cod
There should still be some fish in the upper Merrimack. In my limited experience up there - the best time to fish is in the morning (as it becomes light), or the period from sunset to around 9:30pm. It helps to have some herring around, as that is what they are there for. To be honest I haven't kept too close a watch on what is going on over there this year, but they have had an exceptional run of herring up to the Essex Dam (as compared to recent years), so I'd imagine the stripers will be locked on to them, making big herring patterns the one I would tie on first. In high water - spin fishing gear would be easier, as the currents can be pretty fast and prevent you from getting down quickly with a fly line. Perhaps a quick desent line would be the ticket for solving that problem. I have had very good success with poppers there for the schoolie sized fish (spin and occasional fly), but the bigger fish were almost always taken on larger (9") sluggo's (afternoon or night) or Bombers (at night).
Good luck, sorry couldn't be more helpful (or fly related).