Re: Single hand spey casting
What type of line were you using? I find that when I spey with a one hander using a standard WF line, I cast a lot better if I shorten the head to just beyond the front taper. This allows for a smaller D-Loop because I am concentrating the majority of the mass into the loop rather than the anchor. Having the mass as an anchor kinda sucks because there is nothing to load the rod with.
That being said, if I do cast with the whole head of a WF line, my D-Loop has to be pretty large to get enough line out there to load the rod properly, pretty similar to the video.
Just my two cents.