That's very nice to know.
Generally using elevations strongly decreases the friendly fire effect.
I put my archers on the top of a hill, usually first in front of the spears.
Javelin-Skirmishers even more in front. Slingers I put in the foremost line, slightly to the flanks. It's important that you watch the slingers to prevent friendly fire. They can be really devastating.
Yesterday, with this setup, I awaited a Seleucid army of mainly pahlanxes.
They didn't even make contact with my lines. Fiery and stony death rained upon them until they routed.

R'as