I tried "role playing" as an English army and using 12 retinue longbowmen in a 20 unit stack, although in reality the ratio of longbowmen was even higher. It works great as a defensive because if you put 2 or 3 longbow units projecting forward on each flank, protected by stakes, they just pour so many arrows into the attackers that they have no chance even against your outnumbered heavy inf (whichever you choose to use; I use DEK's with a different animation). Harder to use on the attack though. If longbowmen could replant their stakes I think a stack like that would be unstoppable though. Well, except against a massive rampart with 300 cannon in it.

Incidentally, the English force at Crecy had alot of Welsh soldiers in it, and some "gonnes" (possibly ribaulds).