Paul B, I would use 4. It is more stable and no big deal getting them all level. With 3, and shaking the drum to knock ash off, 3 will make it easier for the grate to fall off the supports. Just my thought bro.
my avatar swiped fatties from the plate....look how sorry he is.
NB Bandera with mods
Weber 22 .5" x 2, 26.75" x 1
UDS x 3
Created "The Great Spam Revelation of 2011."