Bob,
Here are two pics from last years quilt studio project where I used the same windows. Rough 1x4 was used to trim. If you zoom in on the side view you can see where I removed material to allow for the nail fin. This building has solid stain on it which covered the z flashing nicely. The stain on the tiny house does not cover it well but it was never my intention to hide it. It serves a purpose and I don't think it's unsightly. All of the tiny house windows will be seal taped and trimmed, but that can happen later...more pressing jobs to be done.
I hadn't considered an insulated panel over the sub floor. The floor system is very well insulated and when finished will be covered with thin v joint in the living room, cork in the kitchen, and pennies covered with epoxy in the bath. My wife is an artist and the penny idea was hers. It should look cool and at the very least a heck of a conversation piece.
With short wall height, it was a challenge to keep the windows high but not interfere with other aspects. I am tall so they accomodate my line of sight when inside. Trimming them won't be easy, but it seems everything about this build makes one think about every aspect over and over. This is so unlike traditional house building. I'm sure folks reading this have noticed that it's very much a free form build. We make decisions and changes often based on how things are flowing. So far I think it is coming together amazingly well. If you read the blogs and watch the videos on tiny house building, you see no two folks do anything the same.
Thanks for reading and interacting.

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