Hey Dave, some great progress here and looking good.
As to the return edge, it really depends on how much you want to try and reshape that but plate. The less return the easier it will form fit. generally anywhere from 3 - 5 mm return edge is plenty, and in some cases we have troopers that remove it completely to better shape various parts.
The screen used armour had virtually all return edge removed, most probably so the various plates could flex a little more when worn by the actors, but that choice is up to the individual.
Keep up the good work