Impressive, thanks.

ah good ole osprey.

But to be perfectly frank, It does not fully answer my question :( I know all this "how the romans positioned" etc. and I'm not actually intending to realize this formation in RTW. So it all boils down to Polybius not actually telling us and modern Historians suggesting that they just fought in the same way as the romans?
That may be acceptable for tribes with very similar structure(youths, men, veterans) but I'm sure it gets complicated when integrateing tribes with different military tradition, for example would a greek city state sort their hoplites by age and position them like the romans?