just a couple of suggestions...

-if you grind the domed front off an LED the light pattern becomes
broad instead of narrow. that seems easier than trying to arrange
many narrow angle patterns to overlap.

-before you grind off the front, spray paint the entire plastic bit
white. then, after grinding, all the light has to come out the ground
off end.

-the place to get cheap LEDs by the 100s is ebay. maybe 20 cents each
for ultrabrights.

cheers,

Jeff