Different places have different rules, and it can sometimes be difficult to find them out, just like different yacht clubs have different orders for dressing ship.
In
Indonesia, for example, one's flag of national
registration may not be as large as one's
Indonesia courtesy flag.
Normally, one's own registry flag should be at the least the same in inches on the long dimension as the length on
deck of the vessel. By that standard, we should fly a national flag of 48" in length, as 46 in. ones are not made. But in practice, we don't: our
flags are 36", and even then, in some conditions they foul on our
solar panel arch.
As to not flying the registry flag, it probably depends, legally, on what the local's rules are. The flags wear out pretty fast, and it is easy to be caught without. It's not hard to anticipate for a season, or even a year, but on an open ended journey, you may want a flag book and
fabric from which to make the
courtesy flags to have ready to display after clearing in. In our case, we obtained
spinnaker cloth remnants from sailmakers, to use for the fabrics, and one courtesy flag made from that cloth will last about 3 months. If you add a net spoiler to the outer vertical edge, they will go longer. It is always that edge that fails first. Some people consider that defacing a flag; others think it is "taking better care of it."
Ann