Why acrylic when I usually use glass? Because this finished piece is going to be shipped far away and I don't want to risk any cracking of glass.
Here is the upper beams going in. The first version of this structure I made this part with one long beam. I made this one with one lower part, and a long section for the top, for no particular reason. Either way, getting the placement exactly centered involved gravity:
Worked well for the task. Then to secure it into place on two planes. Here also is the second part of the 2nd level wall going in, with window openings.
Here is the tedious process of installing the floorboards for the 2nd floor. Stained, dried for a day or two, then placed in random lengths. When dry, I applied a couple coats of poly for a nice sheen.