Looking at the pictures it looks like he spends a lot of time on the bottom A-arms cutting out oem material and welding in new. I haven't taken any measurements, but it seems like it would be easier to do a single cut across the A-arms, just in front of the mounting brackets, or somewhere along them where you could use a section of square tube the would slide into each section of the A-arm, and weld the A-arm pieces to that. I can't tell if this is what he does than uses plate to reinforce the bottoms. If he does, then I don't understand why he didn't do the same for the top. It certainly seems like it would be cheaper/quicker than making the upper extension, unless he felt that the t-bars would exert to much stress on the welds?

Yes I believe the T100's used the same component as the mini's, just widened the frames. Also until reading this post I assumed that Toyota simple extended the axle tube and inner axles, but now that I think about it that is two pieces/side and not just one end of the CV.