Not to pick nits with your answer but the vertical drop from line of sight would actually be 48 feet ... 16 feet in the first second and 32 feet in the second. And yes, if the sniper is positioned higher on the vertical than the target, the 48 feet figure would be reduced by the estimated vertical difference. The spotter figures all that out.
Helluva a shot in any case.
YUP! I remember Mr. Dowling teaching me that in HS Physics 56 years ago. Of course, that was before "NEW" math, so it may have changed.