What might be the reason for keeping the option to close the sound port? Learning from luthiers, the creation of sound port hinges on augmentation of sonic properties especially for the player.
Years back, I have the chance to remove a spoiled onboard electronic control module from an acoustic guitar. A rectangular opening was left on the side of the guitar. Lo and behold, the player felt the differences in sonic properties and it was improvement to the player. The opening was left on the guitar since…
I have seen some guitars with sliding features to close and open the sound port. My best guess is the sound ports are left opened most of the time. To think of the closing feature as dust protection doesn't make a lot of sense as well. Dust can enter from the sound hole anyway.
Perhaps for training one's craftsmanship… the challenge in making a functional cover as well as one that is aesthetically pleasing should provide sufficient impetus to carry out this task.
Anyhow, best wishes to you in the event you have decide to take on the challenge. Keep us updated should you do. Cheers.
