No, I haven't tried pumice. It might be a good addition to Gritty Kitty...
you should man, it's the best aeration in my opinion, retains more water than perlite, is more dense too.
I have SO much aeration in my mixes, mostly it's pumice and volcanic rock, but I have a lot of perlite from the base vermifire mix and happy frog mixes that I used as the base yrs and yrs ago.
but I have a bunch of vermiculite too, rotten wood chunks, shit I even use little strips of coco wool to keep my soil from compacting over time, aeration is your buddy, that's for sure.
I guesstimate that my mix is about a 50/50 of aeration and compost. VERY fluffy.
you can have the absolute perfect growing soil mix, but if it's lacking in aeration it'll suffer badly, and conversely really well aeration can get you through a very weak mix more so than the opposite... don't believe me? just ask the guys using promix as the base, promix is basicly inert, but that mixed with a teensy bit of compost or manure and it'll grow good nugs, because of the aeration.
But I prefer a mix of all kinds of aeration, that way there are no weak links, sorta my philosophy on nutrients as well.