It is totally understandable to call it shadow system because the way his gonna memories the cards is the same as shadow system, but the way he is gonna learn the image for each pair is different to the major system version of the shadow system.
After certain practice, you no longer need to convert the suit pair into numbers, you will just see them as it. This is what I already tried with my single card system, I trained my self to see the suit’s colour and shape respectively, out of the corner of my eyes whiles focusing on the number of card, and I would know what number it is or what image I had for it if it is: king, queen, Jack. Here’s my result, and thing is, I don’t even practice much with my single digit, system (too many can’t be bothered XD) but because I started trying to see them straight off, my scores improves dramatically. For numbers today I went 80 in 53s even though I didn’t get 100%, but it was a huge improvement upon the conversion speed from numbers to image, because there was, NO.SUB.VOCALISATION.
Though yes, in my opinion, by having the 2 spade pair as 0 has the slight advantage as Ben’s system has been explored more hence more feed back can be given. I personally haven’t decide to have my suit pair as 1 or 0 yet tbh, as I haven’t even finish my new 000-999 system. Just still browsing around and deciding slowly, which is important. Meditation each day helps too, just take a moment to think about the joy of life, then warm up your memory palace after making them. Reuse them after a few days, though I read that Alex Mullen only refuse palace after some weeks XD.
Also don’t be too harsh if you don’t hit your goal, I did that as I made my first 1352 shadow system, and in the end I went lazy and my attitude towards it was really bad, mayby that’s why I find it hard to use it as I can’t recall who is who, because I had stop believing in it. Though I started my new one real fast because I am more experience (I like to think I am), so yeah enjoy the process over the month origen as you make them because it will make all the difference. Dont be afraid to change them too, I know it can be frustrating when deciding to change the old image assigned.