Oh Great Aggregated LAF Mind, I need some advice...

I'm making 15mm Polybian Romans and I'm not sure how to organize them. I've painted up some hastati and principe and mounted them four figures to a 40x20mm base. So far so good! I know that there are equal numbers of velites, hastati and principe and half the amount of triarii but from here I have no idea.

How many bases of each would I need to make a legion? Should the basic units be maniples or cohorts? How many bases would make up a maniple (or cohort)?

As a reference, I have 15mm Successors and I have them organised into pike units of 32 figures (8 bases of 4 figures) and other units of 6 bases with various amounts of figures. I would like my Romans to sort of match them (or should I say: equate with them).

As it is, I have no idea. Please help.