Advice for proper installation?

So I am attempting, to install the multiboard using the video here (I am using this setup with the bolt locking) I have the offset tools to align etc. But even though each individual panel fits along the way, the entire 2x12 board piece I put together ahead of time doesn’t fit. It slowly gets more and more off as I go. I leveled and aligned with each piece install. Frustrating as I have to remove all of the screws and put in wood putty etc and hope I can try again. I don’t know if it’s just an issue of the distance offset having more flexibility to go off alignment etc. But if anyone has a link to a better installation alignment tool or idea. I’m seriously debating just making a parametric tool in fusion 360 to make this easier. It’s kind of frustrating I followed this exactly and failed