I’m glad you like it!
Awesome speed! Congrats!
Man, you already built 3-digit PO lists, so you can be called anything but lazy, haha.
You can use other blocking strategies, like Variable Spatial Encoding or Agent-observer Strategy. You can find them in my first 3-card systems post.
I’d say I did invent it by myself, but this was only because there were other people to helpfully criticize my previous ideas.
I don’t practice speed cards yet, but I intend to use “another” system, which is kind of an extension to D2B. The only person who said to have applied the Double-2-Block system itself was @anon69297051 , but he gave it up for a 1-card system.
Since there are people getting below 20s with the Shadow System, I think there’s no reason to think it wouldn’t be possible for the D2B. In fact, it’s probably going to be easier since it has fewer rules. Moreover, I remember asking @AlexM for feedback when I built it, and he said he did’t find any problem with the method, so I’m confident.