ADA AS has a lot of nutrients in it already, the PS is a PITA later unless you screen it to the bottom.
Folks uproot and the power sand goes everywhere, even if you are fairly careful.
Some get around this by using steel screen mesh between the PS and AS, but why bother......the PS is not a long term thing and some KNO3/KH2PO4 addresses that. Then you have a nice single type of substrate.
More AS would be a much better idea.
If you are really gung ho about adding macros below AS, use Osmocoat, lots cheaper and has the same stuff that slowly dissolves over time.
It's not all ugly pumice that gets pulled up.