After tapping the holes I countersunk them so the dimpled gap cover could be applied.
WARNING I should have done the countersink before enlarging the hole to #36 and tapping, because the countersink bit chatters a little. But it is okay.
WARNING: Not all the holes get countersunk. Holes where the plastic fairing attaches directly do not need the underlying aluminum countersunk because the plastic fairing will be countersunk. So this means the 2 most forward holes and aft holes do not need countersinking because the plastic fairing overlaps the aluminum gap cover. Also this means the cover plates don't need countersinking. Unfortunately, I didn't discover this in time.
I also enlarged the holes in the gap covers to #27 so #6 screws go thru easily.