The windows aren’t the real problem – you can close them with your fingers in a pinch.
The problem is that the pins on the end don’t allow for a mating with the other valve. The location of the holes in the Boston valve determine the inner and outer diameter of the adapter. It’s too big to fit inside the other valve and too small to fit outside.
The solution would be to have the adapter split into two pieces, one with the pins and one without, but that comes back to the original problem of having multiple pieces. If push came to shove I’d rather be blowing up the seats than the packraft.