I’m actually building the 45 degree bar with one wing 12 feet long. I finished the top with 3/4″ oak plywood, and butted an 8 foot section to the smaller 4 foot section, and filled the seam with a homemade wood filler. I used the fine sawdust from some cuts, mixed with wood glue, and filled the gap at the seam. It came out rather nicely. I mean, it is a seam, and you will see it, but with a nice thick finish of eaither Envirotex or layers of olyurethane, the finished top will be fine.