Seems nice and square so far.

I made a structure to attach the frames/transom to. I tried to put that 3/4 " ply on the bottom to scribe it but it would not hold the weight well so I needed more support.

I had to take apart and put together a few times to get it somewhat fair looking. I found that the mid frame must support the weight and let the frames shape the sides.

I think I read that in the instructions but it didn't sink without a fight.