I said that the wood props that were being used weighed a lot. He was using a 90 cm props(~36 inch). One of the most common 36¨ wood props is made by xoar and it weighs 496 grams and he had two of them for nearly 1kg in props. On the other hand a single 130cm (51 inch) carbon E-prop for the Top 80 engine that he was using only weighs 460 grams. So even if he went with two 130 cm E-props he could still save weight.
One big misconception that many people have with counter rotating props is that you could replace say a 100 inch prop with counter rotating 70 inch props or do something like what chrismichaelwhuuuut drew up. Sadly this is not how it works. Its sort of like the difference between two and four blade props, you cant just cut the effective area of the prop in half because you have twice the number of blades. So on may be able to replace a 130 cm prop without 120 cm counter rotating props without much performance loss, but you can´t to go 90 cm props like the person did in the video without major performance loss.