Creating a Legion

Given the 20-unit limit of Total War, playing as a Camillan era Roman, how would I historically go about assmebling and fielding my unitin the traditional quinqunx formation?

http://en.wikipedia.org/wiki/Roman_infantry_tactics

Would I want to have 1/4 Rorarii/Leves, 1/4 Hastati, 1/4 Princepes and 1/4 Triarii (not counting my General, of course), arranged like

https://upload.wikimedia.org/wikiped...Rom-mnpl-1.png

I want to try and use my units historically, and I know most of the secrets lie on the article I referenced, but how to execute those tactics in-game is proving more than a little confusing, coumpounded by the fact the 'hold down the right mouse button and stretch to choose how long and deep your line is and the facing' doesn't seem to work very well in Rome (it just causes a series of single clicks in different locations, which can mean your whole army faces the wrong way or moves oddly. Also, in Medieval and MII, single right clicking makes troops walk, and double clicking makes them run, through whether they walk or run in Rome seems arbitrary, and it seems like they always walk when I need them to run and run when I'm fine with them walking...)

in my opinion about formations, you just need
1x general
2x Eqvites (or Extraordinarii), placed on their Wings
2x Velites (loose formation, on the front without skirmish mode)
1x Missile Troops (Sphendonetai is best, but Mistophoroi Toxotai Kretikoi or Sotaroas aslo works)
4x Hastati
4x Principes
2x Triarii (remember they are supposed to be half-strength)
2x Pedites Extraordinarii (or another local Heavy Infantry) on the wings
2x Hoplitai Haploi, or some kind of cheap local troops helping the Triarii

I would recommend you to use the compositions by Quintus Sertorius here as his guide is probably the maximum of historical realism you can get on RTW engine.

Awesome, that's just what I was looking for, thanks. :)

I am glad that I could have been of some help. I also - sorry my vanity - suggest to consider my own adaptation of Quintus´s rules here. It is always fun, and EB is especially suited for that, to spice your playing with some house-rules. For further inspiration you might want to look in this and this thread.

Also, if you want some peace as your game progresses, you could engage in active diplomacy (no matter how nonsensical it sounds in RTW) to prevent weaker factions from being annihilated by your neighbours: this is my experience in this regard.

Have fun playing EB and enjoy the community on this forum!!!