I have also noticed that I had an easier time on some of the harder levels than the 1 before it. I chalked it up into just walking into the situation where they happen to be weaker. But since I don't know how the skill levels work, I could be wrong. I do know that the ratings here do increase with each step, so people here in general are finding each level more difficult.
Its great you gave this a try. I hope more people do as well, and report on how they did.
Here is a tactical problem from my game at level 7. There is only one right move. All other moves lose badly.
White to move
I watched the very interesting match Hikaru Nakamura played the other day against Komodo 12. He started at level 1 (Computer1) and played all 20 skill levels (up to Computer20). He won all his games until Computer20 where he lost.
I have Komodo 12 and often play against it at home. But I wondered how well I would do against the skill levels here.
So far I have played up through Computer7 without losing, although I nearly turned a won game into a loss when playing Computer7. Fortunately, I was able to turn it around.
I've been doing this with long games (45/45), but you can use whatever time control you like. How far can you get before losing? I did repeat a few levels as warm-ups.