Wow, you guys are thinking about this a lot more than we did
In our previous designs going back to 2010, roll pins are used in the corners of the tube to align them, and everything is held together with threaded rod. The reason then was it saved having to machine end blocks for the tubes. Now it's easier for us to make end blocks, and yet we still like the threaded rod. The frame joint feels a lot stiffer when you can preload it. Is this a significant difference? Probably not.