Hi Lance, so you're getting up to speed on making your first ceph tank a reality. I further compliment you on wishing to create as much a natural home for your animal as you can. I can not help wonder, however, why you would contemplate Metasepia? It is a species thoroughly discouraged to keep, as it is likely rare and certainly from a very, very fragile ecosystem. If you look up our discussions on the exotics forum, you will see that the general supported conclusion (of at least this community) is to "back off" on flamboyants, mimics, wunderpus and the likes until someone gets a proper captive breeding program going, and that's not quite on the horizon, yet.
Have you already received your flamboyant, or are you merely researching the options? In any case, I look forward to your feedback.
Please, remember, even if you would decide, for your own reasons, to pursue Metasepia, do take on board that it's most certainly not a species to start off with in your hobby, even a highly experienced professional such as Thales had an "interesting time" figuring it all out, and that's telling.