I doubt that you missed the major part of the spawning period. During the first week or so of May their appearance in the shallows or other traditional fishing spots can vary considerably with the weather, as in here today, gone tomorrow just because of a cooler day or night. Large female crappies, as with large largemouths, might spawn earlier than the general population, although that is not something that I have read with respect to crappies...but it is something to consider. The recent warm spell, however, should have produced some good crappie fishing. In most lakes the next warm spell should be the key event, but I would bet that in most lakes the fish were not yet fully committed to the shallows. Cool weather sometimes delays the major spawning in larger lakes like Blue Marsh until Memorial Day and the week after, however.
As for Mid-April early May crappie fishing, in general the best daytime locations are in deeper, close to shore locations along steep, rocky drop-offs. These areas are hard to effectively fish with a fly rod, except if an evening bite occurs when the fish may temporarily move up in the water column, possibly following phantom midges, and into the shallows to feed on last year's YOY bluegills or other forage...not spawn. Such deep areas are quite good for fishing with jigs of various types, allowing the jig to sink to the bottom and using a very slow retrieve with thin line (example...6 lb mono may not produce any fish while the guy next to you using 4 lb mono is slaying them). The 6 lb has too much surface area and causes the jig to rise too high in the water column on a slow retrieve. I assume that this may be something to think about with sinking flies as well.
I should add that I have seen such steep sloped areas produce all spring, not just early on, even when many fish are spawning in shallow coves. Dry flies sometimes work well along steep drop-offs, such as lake dam breasts (where legal), just before and into darkness.
I have also trolled streamers in shallow pocono lakes in the last half of April and they have been effective for stocked trout and crappies at the same time.
Perhaps some lakes feature a specialized night bite in your area each year almost as soon as ice-out occurs. I know of one lake where this is reliable, and has been for years. The fish are caught in four feet of water, of which about 2.5 ft is occupied by aquatic plants. The fish are caught for the half hour leading into darkness and for the first hour thereafter. They are caught well out from shore in the upper 1.5 ft of the water column, requiring extra heavy wooden bobbers to be cast in order to deliver very small jigs to the fish.
