Did you count on using less LED's as you went up and down. The
superbright LED's come in packages that will spread the light through a
45 degree angle. Combine that with the need to have less light output
in the up and down directions, and you come out needing only about 10 LEDs.

ok, good idea. but, the more light the better, when you want to be
seen and avoided, so perhpas a you want a mix of narrow angle LEDs
covering the horizon and broad beam LEDs as well.

-Jeff