Another thing to be aware of with NFIP is that if you do manage to get yourself underinsured you would subject yourself to a coinsurance penalty and the claim paid at a discounted ACV rate instead of RCV with recoverable depreciation.
this is why they now require, not request, REQUIRE, an RCE.... to make sure you arent getting into a really bad coinsurance situation compounded by ACV payment ON TOP of coins penalty.