Nice Job on the shack, I hope it serves you well.
The interior is a perfect layout and I have almost the same floor plan as yours.
As far as hole covers; check out my shack hole covers which I made oversize but the original floor holes are screwed under them so no gap ; and then bought the foldable handles at peavey mart and bolted them on; Worked out pretty good.
Also the bunk beds are awsome; Great idea!!!
Enjoy your labour and have a great Hard Water Year!!!!!!