Yep most sibs have a wooden floor board upfront, mine included.
I measured the bow floor and cut a cardboard template to ensure my box would not foul the tubes.
Built a wooden frame.
I never put a floor in mine.
I used adhesive backed rubberised foam.
Stuck this to the bottom edges of the frame / box.
Once clamped onto the floor it forms a really good seal against the floor board.
If im out and its choppy I use my home made spray hood over the bow area.
It keeps everything nice n dry upfront.
That's another project tho