I've never seen the plans for your Extra. But the plans should be the road map of any build not the instructions. Plans vary in quality and plans and instructions do have mistakes. If you have a build or two under your belt there are many common construction techniques or preferences in building that are left to the builder.

Some plans you have to "study" for a while to get a mental picture of how the plane goes together.

I ordered plans for a Ziroli B-25. Great plans...the documentation that came with them was two pages! Something along the lines of "build the wing first then the fuselage. Build it straight or it won't fly right."

I'm studying those plans for a while

Break out the TF plans and instructions and read them. It may give you some insight on the Extra. Sig's kits have good plans and instructions if you want to go that route.