The reason I built Maslow was I got aggravated trying to cut and fit this transom. Trust me, it’s the best part of the boat!
I had only cut the Maslow logo, and a few very small test puzzle joints (more like finger joints) screwed to the center. Finally got the strut mounted to the bottom, a piece of mdf (supposed to be the same thickness as the workpiece, it’s not) layed in on top of that (idea saw here from somewhere (interchangeable bottom panels, I’ll try and find the original thread), 1/4 inch fanfold insulation per @dustcloud, and used #6 gauge 1-1/4 screws (a bit too short) screwed in by my Hitachi 3.6V electric driver (barely enough power for the #6 gauge screws). 3/8 inch marine ply, and as I’m using a table round sled the the thickest I can do at the moment, but that is mostly what I’ll be using.
Watch “Maslow cutting out small boat transom” on YouTube
Edit: interchangeable panel idea by @rocky_creeker