The first scarfer is a 7-1/4" inch worm drive mounted on some particle board.
To scarf cut the end of a sheet of plywood I put the plywood on saw horses and then clamp on a straight edge. And then move the saw tight to the straight edge.
A 7-1/4" blade barely cuts all the way through 3/8" inch plywood.
I need to scarf some smaller pieces of 1/2" plywood (roughly 16" inches by 24" inches) so I hacked an old 8-/14" inch worm drive so it can hold a ten inch blade.
To scarf those smaller pieces of plywood I fixed the saw flat on its side, and then move the plywood over the saw instead of the other way around.
7-1/4" inch blade
10" inch blade I cut the old blade guard off to make room for the big blade (hacked other stuff too) and then rebuilt the blade guard with plywood.