I think the article should stick with the 'unmodded' expansion variants, i.e. an original A500 can have 1 MB chip + 8 MB fast and a 500+ 2 MB chip + 8 MB fast - this is what it was designed for. Where the 9.5 Megs come from is beyond me (sounds more like a 500 than a +).
With some address decoding trickery (Gary adapter) you could possibly add some 1.8 MB Ranger as well. The largest accelerator boards support up to 128 MB and from there on it starts getting hypothetical - of course you could adapt a 2000 board, or build your own accelerator but that's probably extremely rare. All this deviates more and more from the original design and isn't really what the article should be about.
