I magnetised my first 4x4 juxin blue stickerless yesterday. I used inner N45 4x1mm for inner slice and N454x1,5mm for the 3x3 part. I believe it turns out amazing. Can hardly wait to do it on my Wuque. It is very hard to get 4mm in the narrow edge place, but can be pushed in and after glueing it holds even better. I can see that inner slice has stronger attraction comparing to outer slice. But I think not too much for me. It is great, because it helps 3x3 part really to be stable, fast and smooth. I have a feeling that, if you try to insert 50% weaker inner magnets to balance the attraction ,you don't get such a nice 3x3 part. Also, it is great that inner slices stay together for H or Z pll. If someone likes to spin single inner slices a lot, then I would reccomend weaker inner magnets. That means: calculate 50% weaker inner magnets.
After i tried this magnetic 4x4, I understand this new 4x4 records that come from everywhere. The cube feels easy like 3x3.