Never thought I'd be putting these as standard on my instruments. You can flame me at will...
I think if I every made a uke with one I would consider adding little magnets inside and make a thin cover that I could stick over the hole. I would then have the option to close it off, partially open or fully open.
I'd use Very Hungry Caterpillar plush toy when I wanted to close it.
What do you think of this design? The sound holes go all the way around the sides of the body.
...it is a pretty cool thing to try out. Does it have any significant effect on sound projection to an audience? Also did the sides need to be totally laminated or just a load of patches on the inside to keep it structurally sound?