It's the intent of the style of construction of my hatch that the poly top be removeable and replaceable with some ease, i.e., not built in so that you cannot even get to it, so to speak. Also, I need to be able to see over it for steering so its height is important.

Time will tell. I'll post a pic when I have something to show. I've abandon two approaches as not making the grade. Luckily, I had some leftover H. Mahogany in the shop to build the more traditional style wood frame hatch. I was a piece short of building it in teak or purpleheart.... However, when it's finished if the style is a bit too industrial there's some nice 3/8" purple heart the right depth and length to put on as side skirts to give it a prettier look. Of course, if it's pretty it has to be varnished and that leads to its own issues.