By Ro! Designs is one of the specialized up-and-coming independent plus size shops that have proliferated on the web. By Ro! passes the usual checkpoints of a plus size business: they use plus size models, check. They offer sizing up to 6x, check.
By Ro! does have tendency to sell all its items as separates. This does reflect a new trend I’m seeing where people mix and match their bikinis; that said, people still generally buy a top and a bottom, so to me it would make more sense to let customers buy a two piece at one collective price and then let the customers specify which top and bottom should go together; this could even be workable when a buyer is two different sizes from top to bottom.
If you want to know more about ByRo! they have a yahoogroup – it might be worth stopping in and seeing firsthand how these designers work!