Are there enough beads when a bead-based assay is reduced to 5 microliter bead solution on a DA-Bead plate?

Yes. For example, in a 25 microliter bead solution, there are ~2,500 beads per analyte. A 5 microliter bead solution contains ~500 beads per analyte, which is still excessive for the number of beads required for reading, which is generally between 50 and 100.