Just wanted to share my experience- I got the IKAPE Convex Basket on a whim on the suspicion that it would be a bunch of nonsense and I have been proved wrong- the basket gives me lovely goopy espresso. It works really well for medium roast coffees and I think really enhances the sweetness.
I didn’t try step down baskets as it seemed a bit too much faff - but maybe it is a similar experience?
I am having to grind about 10 dots courser on my Niche Zero to (23-25) for a 17g dose.
I tried it on some light roast coffee and wouldn’t recommend it - I use my VST or IMS for that. My only other note is that it is not magnetic which is very slightly irritating.
Just wanted to share my findings.